It's a good idea, but I think it would end up being inefficient, and not from a mana standpoint.

The chances that your one stoneskin every 3-6 GCDs is going to be 100% effective without you timing it is pretty low. My general OT rotation is more like a BRD priority list than a rotation:

0 - Would it make sense to use cover? > Cover
1 - Is RoH on mob? > RoH
2 - Do I have less than 500 mana? > RB
3 - Is the MT in a high dmg phase? > SS MT
4 - Are healers/dps going to be taking dmg? > SS healers/DPS as I can
5 - Am I going to be taking damage? > SS myself
6 - Do I have full mana? > SSs on MT>Healers>DPS>me

I think its a good idea if you want to go on auto-pilot and add a little more utility to the group, but you will get more effective results from being cognizant of what's happening in the battle.