You should get at least 75 spell pen. Otherwise you lose a huge amount of dmg. Even when the opponent doesn't fully resist your spell you deal like 10-20% less dmg on smbd who just has
http://wotlk.cavernoftime.com/spell=69381.
Before you even think about Stam gems you should get at least 1414 resilience which is the soft cap. Personally I never stacked stam gems on my 7sham 3rdudu team because in full wrath gear I survive good enough. Might be a different story when you box only boomkins with no dedicated healers.
My main has 1423 res and 29k HP
http://armory.warmane.com/character/...ecrown/summary
Slaves 1250 res and 26,6k HP
http://armory.warmane.com/character/...ecrown/summary
Never had any issue that toons died in burst before I was able to heal.
In some way SP and haste are actually also defensive stats because they increase your heal. For expl I find
http://wotlk.cavernoftime.com/item=50348 and
http://wotlk.cavernoftime.com/item=54588 extremly powerful because they boost the healing of chainheal like crazy when the shamis have to off heal on AoE heavy fights.
If I'd replace these trinkets with two stam trinkets and stack up stam gems then I'd probably die faster because I heal much less and despite that I'd also deal less dmg.