I don't respec for arenas, I do them as prot
My build is not the usual 49/12 build, but 41/10/10. I do 3v3 and 5v5 arenas only, "casually", to get arena points at somewhat steady rate. And yeah, I have the Season 2 mace too
As our ratings aren't very high, we face all kinds of teams. And quite often, I end up "tanking" rogues and warriors

Especially when playing 5v5. It was so funny to watch three orc warriors charge me, leaving the other healer in our team free to heal in peace

So, when just playing for some points and fun, a tankadin can be quite a surprise for the other team
I have like 512 spelldmg and only 804 healing in my makeshift arena gear, but I've found it to be leaps and bounds better for arenas than my real healing gear (that has too little stamina, resilience and armor).