PvP in arenas has a straightforward goal: make the other time die before your team. In fact this is pretty much the entire game. This can be broken down into three aspects in two general categories.
In the killing category is damage, DPS, attacking, whatever you want to call it.
In the not dying category are damage reductions and healing. Healing is straightforward, it's essentially the reverse of damage.
Damage reduction is more complex and can be broken into two areas. One is mitigating or avoiding damage after it has been dealt. This covers things like armor, resilience, resistance, grounding totem, spell reflect. The other side is preventing the damage completely by in some way controlling the player who is doing the damage. Crowd control and interrupts cover this side. Kiting falls somewhere in between and line of sight can be seen as affectively kiting for ranged and spell attacks.
BoF and snares are a mix of these since they can help to either keep an enemy in range for damage or to keep an enemy out of range for damage.
So where does ret fall in this? It must have some use, otherwise it is... useless.
Obviously ret covers the damage part, but that's pretty common. All damage parts also include some amount of either post-attack damage reduction (almost all classes have interrupts or some form of spammable CC) or healing. Ret isn't especially great at healing, but in WotLK that will change, a lot. But is it enough? I don't see the off-healing abilities of ret being enough to compensate for their weaker damage reduction capabilities in PvP. But they do have some abilities, HoJ, repentance, BoP.
Is ret going to be a sort of hybrid, having strong PvP damage but weaker damage reduction and healing, though still both? I suppose we'll see how it all pans out, but it looks like PvP will continue to be heavily based on CC and no amount of off-healing will fix this. If Blizzard doesn't want paladins to get a lot of CC, how about a lot of anti-CC, preferably that isn't easily removed.
Oh right, I forgot, on the killing side there's also prevention of healing: interrupts and CC. Ret is weak in that area too.