The shadow summoning theme seems rather useless at the moment, the only thing it has going for it is that arcanists can heal the summons with negative energy rays and the such. Even summon monster 3 has only, I think, a +3 AB, though has a truly impressive 72 hp (but they seem to have a solid 17 AC, it doesn't change regardless of the summon level used). I don't think of shadows as the sorts of things that are supposed to tank, though. They're supposed to be feared as their attacks ignore armor and drain the life force of their victims, but as it is they're just a good temporary replacement for your party's tank, or someone to support him in holding the line.
Could they be changed to have less HP (probably half), but more AB?
I dunno. Summon 5 of this theme is actually pretty useful against the right type of foe. Its just not something I'd use on everything.
These themes are supposed to add situational flavor, not to be the 'be all, end all' against every creature type.
Be all, end all? I'm sorry for implying that I wanted them to wtfpwn everything, I don't want that, but I would like for them to be less based around toughness and more on what they are generally known for, which is their generally poor durability but deadly accuracy. I don't care much for situational flavor when an axe is cleaving off my head and I lose a weeks' worth of work and all my gear (or worse, I die in some crappy random PvP and lose everything, which could quite possibly happen as the shadows are undead), because my summons are crap even when I throw everything I have at a foe.
I've made some adjustments, but don't expect too much - this is another theme where the base line summon just gets "leveled" up.
*cough*
http://www.escapefromunderdark.com/forums/showthread.php?t=39128
*cough*