I played RoA when it came out years ago. I just stumbled over it again and started playing and thought about using some of the non standard archetypes. Nevertheless I'm having some problems with some warlock/witch spells, basicly summon crows and terror broom.
Sometimes summon crows does dmg, sometimes it doesn't. Does the dmg increase with higher skill lvl (I doubt that) and how much dmg does the terror broom? I encountered the brigands in the imperial fortress and the spell succeeded (+ the animation is shown) but I can't see any kind of dmg which is quite annoying. Has someone played a warlock/witch character and could give me some tips about the spells?

Alot of the spells that have been added from the original Dark eye game are either nonfunctional, or function differently. Terror Broom Animates the witch/witchers broom, and the raven spell summons ravens at your enemies. I believe the number of ravens is incresed the higher your level is. It depends on how you made the three necessary rolls to succesfully cast the spell. I can just recommend you to level up the useful witch-specific spells over the course of the game, and have the rouges and warrior classes defend them. I had a witch and they can be leveled to powerful Summoners. Witch's spit is the witch version of balm which is more of a multispell, It gives back health, and neutralizes poisons too. Level that one instead of Balm. Witches knot is supposed to create a barrier, haven't tried it out yet, it supposed to create a illiosunary barrier to defend from enemies. Ill try some out myself.

I played this when it came out years ago and I mostly played non standard characters (because I was familliar with the pen & paper). I played a witch, but as far as I remember those spells where not particularly usefull (it was still a good character). On the other hand if you have a mage speciallized in demonic invocations, at first he would be VERY weak, and NONE of the spells would work. And after leveling up for some time the spells would start to work, but the demons TURNED ON YOU. Only after reaching very high levels, possibly after importing your characters to the next game were you able to control those demons and it would be the most powerfull character, actually overkill.