Are you 5 boxing them all? or just controlling a healer and another person is running 4?

I'll just give some general paly healing advice in arenas based on your questions:

a) The pillars. Depending on your rating, you will more than likely be the burn down target for a lot of teams. Most will bust out the dps to get you to burn your bubble, then focus on your shamans. I say use the pillars because this allows you to los their dps. If you are 5 boxing, stick your shamans in the middle of the arena (near the altar, under the bridge, or in the middle circle), and dance around the pillars, only popping in to heal.

b)HoJ is an excellent form of CC. If you are facing a 4dps squad then wait until you get one of their targets to 20% health and then hoj their healer. The tactic you suggested is not what HoJ is designed for and will put your paly at risk of being singled out. That tactic is usually reserved for fears and cyclons (the dps charge in and the warlock charges to the back of their train and aoe fears the warriors support while the rest of the team takes out the warrior).

c)This will greatly depend on what type of team you are facing and your rating. As a general rule of thumb, take out hunters, shamans, and shadow priests first. I rarely, if ever, will call out a warlock as the burn target, unless they are UA or destro spec. Warlocks, even with crap gear, are just too well equiped to take dmg, especially from casters. If you are facing a 4 dps squad, take out the squisher target, while your paladin goes and hoj's the healer. No way you should not be able to burn down 1 target with 4xele shamans and a hoj'd healer. Survive the initial burst dmg of a 4 dps squad and you will win.

d) This type of team is a blessing and a curse. Blessing in that they will die instantly with one chain lighting rotation. Curse in that it is a multi box nightmare. This team survives on the ability to LOS their opponents. my advice would be to rush in and pop your instant CL on their cloth healer or cloth cc (warlock, pirest). Avoid mages and paladins though (ice block and bubble)

I hope this helps