Jetbikes have a large footprint and their assault move is on average 7 inches. Not alot of maps have LOS blocking terrain and even if you get some. S6 os great if you are shooting MEQ. Try shooting TEQ and tell me how it goes. The bikes themselves are MEQ and very easy to kill. As soon as they jink their shooting is gone. low leadership. They are by no means an instant win unit.
Jet Bikes fit on a roughly Terminator sized base, using the current stands. I can hide 5 Terminators inside a 5"x5" ruin. Or a dense forest, or a medium sized hill. If you play with minimalist terrain, that's the meta you play in, not the fault of the Bikes. Plus, at long range, you're only able to be retaliated against by "Big Guns". 43" range guns to retaliate? Exactly how much is this happening? You're certainly out of range of bolters, gauss, and even Tau rifles. And like all Eldar units, they're specialized. They're not good at killing TEQ. That's what D-Scythes, Fire Dragons... Bladestorm... uh... Other D-Class Weapons... Spider-guns... basically every other pine-cone-inserting gun you have at your disposal is good at killing. Wah! I have one target that my super-balls-out amazing unit isn't good at killing, so obviously it isn't the most disgustingly broken troop choice in all of 40k.
The wraithknight is so easy to kill.. All you need is: a unit of cents Ina drop pod. Maybe some skitari Ina pod. How about tau long range d weapons? Or simple volume of dice.. Its not like he is armour 13 with a 3+ invul..
There is one unit that annihilates a WK. One. Singular. Unique. Hard counter. What's a WK good at killing? Um, Everything? Is there a target the WK isn't good at killing? You spend more points on a Drop-Grav-Cent squad than you do on the WK. That DGC squad typically inflicts 8 or 9 wounds on the WK. Which means that, typically, if you're in 4+ cover you will survive... barely. Yes, other squads will probably be able to finish you off, if you've left yourself exposed... but it not? You'll mulch the Cents. Or move away from them. They are slow. No, he doesn't have Armour 13 with a 3++. Instead, you have an armour save all around. And nothing spontaneously inflicts extra wounds, like an "explode" result does to a Knight. Trust me, I've killed plenty a Knight, and that almost always factors into it. And you can still have an Invul. And you don't need to spend over 1200 points on a formation to get that bonus to your invul.
1200. points. 4 WK for that. And those D-guns pounding those Knights before they can reach you. Sooooo sad for the WK.
My big issue is that 90% of eldar are weak fragile dudes who die very easy. You can say well, use range but we don't really have the best gunline around.. So we got the WK, the one model we have that can soak up some fire and we cant even take more than 1. Yet you can take 5 knights or spam 6 helldrakes, 3 riptides etc. Every tourney is saying 1 WK but its just hate at eldar.
Eldar have a poor gunline. That's because they are a gun-wave. Flowing around. Refocusing their shooting. No good target? Move across the board in one turn! You have the kind of firepower that I, as a Guardsman, would weep for. On a MEQ platform. Moving like a dude that's strapped to a Jet Engine with a rudder.
Have you ever considered, that Jetbikes put out more hits per point than Imperial Guard infantry?
250 points of Guard will, at 20" range, achieve 25 hits on average. With Lasguns. And they move like molasses and have a GEQ statline.
243 points of Scatterbikes will, at 20" range, achieve 24 hits, on average. With pine-cone-ramming Scatter Lasers. And the move like the wind, have a MEQ statline, and can decide to Jink, if they are so inclined.
They're shootier than Guardsmen. I mean, what more do you need? You have the best gun-wave around. If something gets close, you hose them down with D-Scythes. Or Shuikens. Or you stomp them to a fine red paste. Or you just move away.
The loss of WK in the competitive environment is likely a response to Grav. Nothing else in the Eldar army suffers so greatly at the hands of what's a pretty obvious competitive choice. So you remove that singular ideal target, and you neutralize 300 points of your opponent's army. That's comparable to the 5th edition Mechanized craze, that saw people eliminating the usefulness of "Basic weapons" by running armour. Meltaguns were important to the meta, and you could run a counter-meta list by running Ork Hordes, for example. Cooking an Ork Boy with a Meltagun is a kick in the 'nards. Same deal with removing high toughness, good save models from a list. Take away a Grav's ideal target, and you're in the same boat. "Ok, I'll try to grav your Wave Serpent. Derp, you jinked." That would be the reason for WK's disappearing. Not that they aren't good, but because if you take them out, Grav Stars are greatly diminished in value.
It's not Eldar "Hate". No decent player "hates" another player. They can recognize a complete disparity of quality in codices, and will take effort to somewhat neutralize that disparity. It's not unreasonable for a player to wish to have a chance of winning, despite not bringing a top-3 dex. And there's a big stretch between the Top 3 and, let's say, number 5.