I also found most of the things in the citadel to be relatively easy. The DK patrols were tough, and there is a ghost you can summon that can range from easy to quite difficult, depending on who gets the first hit in and whether you/it miss a couple times or hit consistently.
The traps in the hallway past the locked doors could kill me, but the summoning doll volunteered to go first.
I collected some alchemy plants, but didn't bother trying to create any potions until very late in the game (to make some permanent potions after buying holy water from the BF merchants).
You can learn higher levels of Repair. In act 1 the weapons officer in the drill grounds teaches it to level 5, and Brian in the BF teaches level 6 (in later acts he teaches higher levels).
The act 1 summoning doll can equip a crossbow, so kept out of harms way it can provide support for tough fights. Most of the time I just used it as a mule, but it came in handy once in awhile. Even when upgraded the summoning dolls do not get as strong as the main characters, though, so don't last particularly long in melee fights. They can help, though, and at least provide a distraction.
When looting I would activate a summoning doll and leave it in place, then continue with my main characters. Anything I would just sell I could drop directly on the doll's portrait, keeping my main characters unencumbered longer.
There is a skill to increase the range of the dolls, but I didn't bother with it until the after-game battlefields, which I didn't play for long.
The lock level for some of the barrels does seem a tad high. Some people collected locked barrels and stored them in the BF, so they could hopefully get them by the end of the act if they increased their Lockpick skill enough. I pretty much finished my first game before the patch was released that fixed Lockpick, so didn't have to worry about locked barrels. Too bad you can not just smash open locked barrels like you could in DD (though if it is trivial to do so that does kind of defeat the purpose of locking the barrels in the first place).
If you want to try solving the quests in the citadel you can go though wearing the citadel guard armour, and when you are done, remove the armour so everyone remaining turns hostile when they see you.
