OK let me explain something to you about the mechanics of Blizzard itemization. Each item has an item level (not the same thing as the level needed to use it). That item level determines the amount of stats on an item. Greens always have lower ilevels than blues, which have lower ilevels than same level epics. Season 2 arena gear has a higher ilevel than season 1, therefore season 2 has higher stats on it.
Now, knowing an item has a certain limited amount of stats on it, based on its ilevel, you see that arena gear has resilience on it. Because it has resilience on it, it lacks something else that an equal ilevel item would have. In the case of arena gear, it is mp5. Mp5 in arena is all but useless, therefore it is a waste of the ilevel points to have, and Blizzard did not include much (if any) mp5 on arena gear. Therefore, if you try to use PvP gear, you will seriously hurt for mp5, to the point of possibly causing the death of one of your raiders because you didn't have the mana to heal them.
Other classes can freely use PvP gear as a starting point for raiding. DPS gear is DPS gear is DPS gear, after all (though PvE gear will do more DPS in a raid). However, for the paladin class, we do not have the option of using PvP gear in raids. Any paladin that does, probably has a terrible amount of mp5 and won't be able to heal in extended battles (which don't happen in PvP. When was the last arena fight you did that lasted 15 minutes of continuous, non-stop, healing?) I'm glad that you are seeking advice from multiple sources, this shows you have the potential to learn from the more experienced people and will probably go far in this game. However, I'm telling you from experience, and the above listed reasons, you do not want to use your arena healing gear in PvE, ever.