ok, did a few test runs on destroyers. They are definitely anti-Meq now, the most painful thing for them is their range now though, it feels so short. I want to keep them behind most of my army and preferably in cover as a couple of krak missles will easily decimate a squad, negating RP rolls. better AP in exchange for less shots, lower strength and shorter range made them much more niche. still, with the number of MEQ armies around they are neccessary. A squad of 4 or 5 is pretty important against any marine army, and if you get to unload on a footslogging terminator squad you will shred them.
I am definitely loving Scarabs though, my opponent didn't want to move his rhinos near my army because I had a swarm of 10 hiddin in some woods nearby lol, he eventually has a squad charge at them to tie them down so that they wouldn't devour his vehicles. Once your opponent knows what they can do they will definitely either direct some fire/forces to tie them down or take them out or they will make their vehicles take a longer path to reach you to avoid them. they are perfect for stopping a blood angle land raider/rhino rush.
Havn't tried wraiths yet, they really do get pretty expensive with lash whips, so I couldn't fit them into my test army. I just feel that if I need close combat bruisers the spyders are a better buy, 5 more points than a lashwhip wraith, they are much beefier and you get at least 1 free scarab from each of them which is essentially a discount in points. heck, if you somehow keep a scarab swarm nearby for 3 turns they can pay off their points cost just by making one each turn. main downside for the spyders is they are slower and lack an inv save.
If someone does a solid test with wraiths let me know, I can see their potential, it's just the fact that lash whips are pretty much mandatory for them to be effective hurts quite a bit. Now, on the other hand if the enemy has come to grips with, say a squad of your lychguard you could send some wraiths over to join in just to slow down the enemy troops so your lychguard attack first, that could definitely be a huge boost in close combat.