Actually, those are in there to PERMIT defensive builds, not to kick a55.
I have a pure Stamina mage with Blood Shot, Master Rifle, the Minotaur Set, and Spiked Armor. OMG, it's amazing. True I don't blast away groups at a time, but I pull creeps off of NPC then watch them die for attacking me (with over 5k health and 50 hp/sec regeneration).
Also, Mana Shot ( especially if you go for the Mana Set, i.e. Mana Shield ) is basically the same on the other spectrum of the game. ( Like using Sacrifice Shot with Mana Shield active ).
In my opinion, they are already the best builds in the game, focused more on tanking and Boss rounds than mass destruction as a power Metacian is. Without one or two of them in your group, you will NEVER make it to the Infernal, or past other levels you probably haven't seen yet.
( Also remember that the Locust Shot, arguably the highest damage dealing Shot in the game, is based off of all 3 stats equally! GO ROYAL SET BUILD! )