Quote Originally Posted by 'Mercurio',index.php?page=Thread&postID=95315#post 95315
There is no cap on spell penetration, but all the spell penetration in the world does absolutely no good unless your target has resistance to the school of magic you are casting. I haven't worried much about it, but gearing up for PvP normally has given me a spell penetration of 44 (+20 from cloak enchant, +10 from Veteran's Band of Dominance, +14 from Vindicator's Band of Dominance). This is usually sufficient, because most players won't wear resistance gear into the arena. The common resistance buff is MoTW (the druid buff), which gives 33 resistance to all schools of magic. Night elves have a +10 nature resist racial passive as well, but my spell penetration of 44 covers both.
70 would be the "cap" on spell penetration for buffs. Aspect of the Wild or Nature Resistance Totems buff 70. Hardly anyone will gear nature resist gear for arena, but a smart team will switch their buffs when they see 4 elemental shaman.

That's one reason I don't bother with frost resistance or fire resistance totems in arena. Most casters easily get the 44 as listed above. and having 36 resistance seems silly over whatever totem i'll have to give up.

Note: None of the buffs stack, so MoTW doesn't stack with either of the above. However, we do get kinda screwed in that you can't purge off Aspect.