[Taqwus]

The one obvious issue would be -- how much are you giving up for that level of magic? Two nines is usually pretty expensive, although some combos are more affordable than others due to the pretender selection.
It can work, and you can get some outrageous blessing combinations (Fire 9/Blood 9 would make for ludicrously offensive-minded Lava Warriors in addition to being thematic; although the Blood 9 blessing likely isn't worth going past 8), but whether it'll help depends on things like size of map, indy strength, sacred unit types et al.