Spiritmasters are a unique class, in that much of their power is actually derided from the abilities of the elementals they have learned to summon. I have known this to cause a degree of stigma from other Daeva as the power they wield is not really their own. However, that is not to say that Spiritmasters are weak - indeed the extra protection granted by their summons makes them far more durable than Mages and Sorcerers.
By all accounts, the path of the Spiritmaster is one of the more testing paths to journey down. While they start out with limited actual ability, their potential is great and is only unlocked as they become more experienced, eventually granting full command over all four elements.