As Alerian (and others) mentions, many STR 6+ shots will also take down Greater Daemons/Daemon Princes no end, especially Doomed ones, although it may get more difficult to kill 2+ Saves Tyranids, a too common occurence.
Alternatively, some Starcannon Warwalkers, although pricier, work well to take MCs and Feel No Pain models alike, although I never tried them myself.
But I wish to delve a bit more on some other ways to kill MCs here, please bear with me...
For Iyanden players, combining those two elements to take on armies which make use of Monstrous Creatures seems like a pretty good tactic to me, but I'll let Starrakatt et al expand on that one.
What are you, a prophet?
Rangers/Pathfinders can still work too, and against Chaos they are less vulnerable, as they won't be coming down from the skies in Drop Pods, making it easier for you to protect them.
Much so, although I would add the Harlequins to the vulnerable units to Deepstrike lists, as I found out recently - Academic knowledge is nice, first hand disaster make you learn...
While rending isn't as potent as it was, it's still one of the best tools the Eldar have for dealing with Monstrous Creatures.
And Doom is an absolute must have if you decide to use our Snipers and local Clowns to get at MCs, but not necessarily worth it if used 'only' to help them. But then, there's plenty of (relatively) low strength units/guns in our armies (Troops and CC stuff) that can benefit of that power, so...
Another thing to consider is that both of these are highly vulnerable to fast lists and/or drive by rapid fire (include Flamers) squads in addition to the Deepstrike lists, so you when you build your own force you really have to take this factor into consideration and make heavy use of synergistic units to protect your investment - The reason why I am slowly relegating my Rangers/Pathfinders as supplementary units for bigger games as I want to keep my lists entirely mobile for that purpose.
The other options are to take the Avatar and close assault Wraithlords, and go Monstrous Creature hunting that way, or you can take Wraithguard and hope you get the chance to shoot them with Wraithcannons.
How nice of you Irisado, my very favorites, thank you.
Consider this list, which include many of the units listed as very good at taking out MCs (and all will understand why I do not have much problems with the biggies):
HQ: 145 Pts
- Farseer W/ Spirit Stones, Runes of Warding, Fortune & Doom – 145 pts
ELITE: 190 Pts
- Harlequins X 7 W/ 6 Kisses, Shadowseer & Death Jester – 190 pts
TROOP: 802 Pts
- Wraithguard X 10, Spiritseer W/ Conceal – 396 pts
- Pathfinders X 6 - 144 pts
- Avengers X 10, Exarch w/Dual Catapult & Bladestorm - 152 pts
+ Wave Serpent W/ Twin Shuricans, Spirit Stone - 110 pts
HEAVY: 290 Pts
- Wraithlord W/ 2 Flamers, EML & Brightlance – 155 pts
- Wraithlord W/ 2 Flamers, EML & Scatter Laser – 135 pts
FAST: 70 Pts
- Vyper w/ Scatter Laser & Shurican
TOTAL: 1497 Pts
Last time I played Bugs with this, both Wraithlords engaged respectively a Tyrant and a Carnifex in CC, one being eventually killed by the Tyrant (not before taking 2 wounds of it) and the other slaying the Fex. Then the Tyrant got erased by the surviving Wraithguard that I used to hold off half of the Tyranid army while the Harlequins killed the swarms locked in CC with the Wraithguard by the dozens with Fearless Combat Resolution.
The Harlies died afterward to a Dakka Fex, but then my opponent had to chose between Assaulting the Wraithguard or killing the Harlequins - He chose the clowns then the Dakka Fex got Wraithcannoned (new verb!) to death.
Rangers/Pathfinders traditionally performed well enough for me against MCs but were of little use this game as I used them more as a bait unit and to camp an Objective.
It's not anything that I have personally tried, but to get around the short range of the wraithguard 5 could be mounted in a wave serpent with warlock. Could give you the potential to get near a big bug. Though for the points you may as well take fire dragons. Has anyone ever used wraithguard in tanks?
I do often enough, although with only 5 shots against 4 wound MCs is stretching luck to the extreme. Best to use them to finish off the wounded ones. A good choice for me is mounting Yriel with them - Increase their versatility in AT, CC, anti-MC/MEQ/Hordes capabilities to a surprising level of hurt when taking into account the option for him to leave the WG and bomb almost any unit with the Eye of Wrath...
Note that by using Yriel or one of the high strength Phoenix Lord (of which I found Jain Zar complement the Wraithguard the best) you palliate the unit's weakness against CC retaliation from the MC.
Wraithgaurd aren't a bad choice for sticking in transports but it starts getting very pricey after awhile and once the MC dies they dont have much to do afterwards if you are against nids and they will probably be far more expensive than the MC they are killing anyway a 5 man squad with a tranport come close to 300 points where as most carnifexes arnt more than 200 pts.
And that is the crux of it, especially if you invest in a pricey charcter to lead them, which lead us to this:
...another problem as with the Fire Dragons is the range problem as even though they are much tougher than Fire Dragons they are twice the points and will be quickly outnumbered and killed.
Fire Dragons and Wraithguard in a transport could be great MC killers if the enemy player was dumb enough to leave his MC's unsupported and exposed somewhere but unfortunately that doesnt happen often enough in my games
It means that if you decide to use mechanised Wraithguard you effectively have to build your army with that particularity in mind, either by going with a mostly mechanised force (then a Fortuneseer nearby would be invaluable for the Wraithguard) or with a mixed list with the appropriate mechanised and/or footslogging/long range backup to support the fast part of your force.
Without delving deeply into mathhammer here, lets consider this mechanised Wraithguard/IC unit:
ELITE/HQ: 510 pts
- Wraithguard X 5, Warlock W/ Destructor - 210 pts
- Jain Zar (W/ Executioner, Silent Death, etc...) - 190 pts
+ Wave Serpent W/ Twin Shuricans, Spirit Stone - 110 pts
Advantages (vs 10 WG on foot):+A) This unit will dish around the same amount of damage to any MEQ unit as a full volley from a 11 strong WG unit TROOP (Spiritseer included).
+B) Should inflict MORE damage to any Horde unit due to Destructor.
+C) Much meaner in CC against MEQs and MCs due to the IC's inclusion, about equivalent against Hordes.
+D) About as resilient than their 11 strong unit counterpart, and that due to Jain Zar's superior save, particulary with wound allocation from shooting (Majority Toughness rules!)
+E) More mobile, versatile and abilty to contest far in th enemy DZ.
Disavantages:-A) Very high pts cost.
-B) Harder to support.
-C) Fortuning them effectively mean adding more points to the fray, usually meaning flying the Farseer in another transport - May as well make a full mech force in that case.
See HERE, second list.
-D) NOT scoring.
As you can see the cost is steep if you add the PL, but it quickly decrease if you decide to use Yriel or a standard Autarch (W/ Fusion Gun/Powersword - 90 pts) but the lesser the IC, the lower the unit's resilience will usually go down, along with CC potential (although Yriel is usually even better than a PL to inflict hurt).
So yes, while a mech Wraithguard (or Dragons) effectively expose themselves to many a nastyness once disembarked, there are ways to counteract them to be overwhelmed if they are given adequate support and backup, either from afar or close by with fellow mech unit(s).
The important thing to remember is to build you army around the concept of mutual support, especially when dealing with very expensive units - as we should always do as Eldar players, whatever what we use.
Sorry for the long winded speech, hope it helps.
Starky