pls don't wasting your time on stoneskin... the only use for it as SCH is to precast it before fight and only if u'r running a 4 man or a 8 man without a whm... also paladin can do the same as u since they also have access to that skill (true to be told not many pala feel like lvling a conj that hig... and I can't biase them on that...)
as a WHM myself I find it only usefull when i need to give a specific member of the party an hp boost before a specific phase (and that only if I feel that he have too few max hp due to death debuff or feel like I will not have time to top him off right after the phase...)... but with the same mana and less time a sch can do the same (or better if he crit) or with double mana and almost same time (with spell speed buff from faire) on 2 target or one target + lesser aoe shield on the rest...
SS is really a poor skill for non WHM... and still situational for WHM (situational as for uses out of preshielding before fight begin that is a must have for our treat generation)
on the other side... 26 lvl as THM are really a must have... thee are so much uses for that insta cast that I discover a new one every day... and the 60 sec CD is really short... well if it was shorter it will be even better... but it is already an OP skill as it is ^^'
PS: for those that prefer 2 WHM to WHM+SCH ... they didn't have the chance to test what those 2 healer combined can do or had a really bad SCH (but really really bad...) with them once and jumped the gun deciding that all SCH are the same... or else are reaaaaally poor player that can't avoid a single avoidable aoe and need a constant double med II on them... that refull them faster than med II + aoe heal+ shield... but put much more stress on the healers... and for those that think that double regen on the tank is OP... they haven't seen what a regen + critted shield can do... With the SCH i usally run around when she crit we can both swich off from tank healing and take our time toppin off the group or simply reccing mana or even trowing out some dps...