Regarding #2: Depends on what you are raising. If I raise a giant that I killed then it's definately more powerful than any summon.
well yeah, but its also not usefull because you most likely dont have a full dungeon of giants in front of you. What I mean is: most giants are either on their own or 1-2 of them together, and in the outside world. Kill one, rez it, and now you got nothing to use it on.
In dungeons and keeps, most ennemies will be, at worst, trolls. And even those are kinda rare (i have seen ONE cave with em, and even that had a grand total of three).