So, after a conversation between The Lurker Below and I this afternoon, I decided to test out flyers using my two valks (as vendettas); and, I have to say, people don't need to be as worried about them as they might be. I mean, they're still great, but the fact that they move a minimum of 18" and can only turn 90 degrees beforehand really limits their weapon LoS.
Valks, vendettas, and, in some cases, storm talons, have an advantage because they can outflank when they first arrive, which means you can bring them on from a short table edge to maximize the time they stay on the table no matter what the deployment. But in order to reliably disembark troops and avoid going off the table they're going to have to go into hover mode (or, in the case of pure flyers like Necron night and doom scythes) just go into ongoing reserve, which means you're losing a turn of shooting. If stuck with long edge arrival I'd send them out from a corner to travel diagonally across the board.
In my test I pitted two counts-as vendettas against an AC dread, tactical squad with MBs and ML, LR, and aegis defence line with quad gun. I outflanked both but only one arrived on turn 2 to take out the quad-gun. The twin-linked fire from the LR was pretty effective, forcing one to jink to avoid being exploded but the dread couldn't hit and rend and the ML couldn't hit at all until they went into hover mode. By the end of turn 5 both valks, which had gone into ongoing reserve once, had only just managed to wreck the LR after pounding it with LC fire. LRs are pretty darn resilient in this ed, so long as they aren't assaulted, and their twin-linked LCs aren't bad as AA in a pinch. I put the vendettas into hover mode for a few more turns but that makes them super vulnerable to shooting and assaults.
So, flyers are fun and good but they certainly have their drawbacks. It's pretty hard to hit rear armour and you overrun your targets distressingly quickly. Keeping targets in 45 degree LoS from all forward facing guns is very hard for more than one or two turns, then it's either into hover mode when very close to infantry or into ongoing reserve and miss a turn of shooting. And if your flyers are angling for the same target and it gets destroyed it makes it hard to fire all weapons at another good target unless they're nicely lined up in a row.
Krak grenades and MBs now seem even more essential so you can take advantage of momentarily vulnerable flyers in hover mode. Also, if you're worried about a lack of AA, take anything that's twin-linked with a high S or that rends. That'll give you a decent chance to actually hit and at least glance flyers.
I'm sure flyers will be even more annoying (read: effective) when part of a mixed force but I don't think they're going to be as OP as a lot of us were fearing.
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