Just as a point of correction, the EUK list doesn't only change the HB and FD exarch weapons:
- Howling Banshee gets First Strike
- Dire Avenger gets MW
- Fire Dragon gets MW
- Shining Spear gets Lance
The remaining four get their "normal" extra attack, with the warp spider's being first strike as a result.
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I think it's pretty clear that there will always be some aspects (and exarchs) that are suboptimal, and not always just because of their specific stats but because when you are limited by points, you have to make choices and need to take units that fill certain roles or are more flexible. Howling Banshees are just a niche unit. If we could go back in time to change hit allocation and include a power weapon rule in the rulebook it might make sense for the banshees. But IMO it's not worth inventing these special rules now to "fix" the unit, because they will never be "fixed" (or if they are, then something else will be broken instead). Giving the exarch first strike is worth doing IMO just because it is annoying that they don't have it. It makes the list, and the way they play, feel strange. You could also test Infiltrators. Doing those two things would IMO make them really good in their niche, but it won't make their niche any less "nichey" and thus I won't pick them any more often than I already do. By now I have just accepted that and moved on, I use them occasionally as a cool unit
