Alright, think it's been long enough to determine that no-one has anything to say on sentinels. I think it's natural to move on to destroyers from that.
Obviously, the archer skill tree is the same for both of these, only thing to really note there is Shootdown again, longer cooldown on that should do. And maybe adjusting the hitbox, it does seem quite big compared to the animation, but that might just be me. Only useless(ish) skill on that tree is Bow Mastery, it could use a small buff or maybe a change to be % based. It's meant to be a skill to boost damage in the early game though, so it can't be too powerful.
In terms of the destroyer line skills, I think the class is fairly balanced with no major issues. In terms of skills that aren't very strong and could use a buff, I think Carpet Bombing could have a faster cast, that one at least is very hard to hit, and when you do hit it, gives very little reward for it. Other then that, there's a few dots in there that are useless again, fire grenade, Caused (should it be cursed?) bomber, and N2 Ammunition Strengthen all have basically useless dots. And afaik, Accelerator Tuning is the only other useless passive there.
Aerial flurry is one skill that I think is just badly designed, especially with Shootdown around. Dunno how to make that work better though, any ideas?
One interesting thing we get to with Destroyers are skills that are blocked in pvp. As I understand the team here want's to be able to nerf skills in PvP only, so that these skills could be unblocked. Well, in the case of destroyers blocked skill, Camouflage, there's many ways to balance this (and other hiding skills to that matter). First thing is a long cooldown of say 2-3 minutes, that has to happen. Then there's 2 options I see: either make the duration be a bit shorter, or have the skill drain a whole lot of mana while active. Hiding skills are an interesting thing that one can use to their advantage for example to ambush people in group pvp modes, think they would bring an appealing tactical element.
As I said, I think destroyers are quite balanced in pvp and pve, so they don't really need any major changes in my mind. As always, I can't really say anything about the chain combo, but I don't think there's a problem there either on this class.