i agree actually. shortbow was fine if the aoes and combos are used proberly.
i usually used pistol+dagger just for situations in which melee seemed to dangerous, doing damage and crippling with DD, 3-slot to keep range or dodge (it works great to just let big enemies like ettins run up close to you, then shadowstep back and see their slow melee spells hit the dirt) and in between that some 'auto'-hits when i had no initiative to spend. 2-slot when i was in bigger groups, for the vulnerability (it's damage seemed actually lower than 1-slot, so not really worth using in single or short fights).
pistol+pistol certainly would do more single target dps, but it sacrifices too much utility imho, especially with DD doing way more damage than any single pistol shot anyway, in addition to it's other benefits.
yes.
thief felt a bit underpowered (in pve) in general, but not by a large margin. it gets a lot better once you have all your weapon sets and their dual skills, as well as 2 or 3 utility spells that you like on your bar. and keep in mind, every class is supposed to take up quite some defensive stats on gear as well. it really helped a lot when i got some nice vitality stuff at like level 12-18, as it increases your health pool significantly in relation to the small basic pool of thieves.
still, thieves will always be meant to be more of a damage avoiding class, rather than a damage absorbing one (like warriors and necromancers). for that purpose, you get a lot of mobility and various different evade and escape mechanis, as well as other things that help with hit-and-run-tactics (or rather burst-a-bit-and-then-try-not-to-get-your-face-flattened-for-the-next-few-seconds-tactics)^^
i really like the stealth'n'heal mechanic actually, because you can stay in stealth for ~2 seconds and regenerate initiative and cooldowns (as well as various other benefits with the right trait build on higher levels), without resetting an npc, as well as having additional burst and maybe even cc for free with your stealth skills