I've been to Arena Junkies and SKGaming, so I know there are very high level Holy Paladins rocking it in PVP. I just am not one of them. Throughout the weekend I jumped back and forth between my Resto Druid and my Holy Paladin and healed various battlegrounds. Admittedly battlegrounds are much more free form than are arenas, but the act of healing is the same in either case. I understand that there could potentially be more people beating on you in a battleground than would be in an arena, but one good Rogue can just ruin my day on my Holy Paladin. He can't -- or at least I haven't found one that can -- on my Resto Druid. Holy healing is fantastic if you're left alone because your bomb heals can quickly replenish someone who is nearly dead. And you can intersperse FoL heals amongst a group, keeping yourself healed with your beacon if need be.
But when you are not left alone, and when your being beat on by two or more people it really becomes an issue. I hate having to stop to heal, and with only one instant cast healing spell that has a six second cool down, you end up having to do that quite a bit. PVP is a exercise in mobility, and being immobile like that not only attracts more attention, but makes it easier for them to kill you. It also makes it harder to heal your team mates as they themselves move. In Warsong Gulch its a pain to heal them as they move back across the field as the act becomes akin to heal, then hop. Heal, then hop. Except in this case it's heal then run ahead a few seconds, then heal again. Too much can and does happen in those precious seconds when you have to move. Of course, if the group stops and is somewhat static for a bit that isn't the case, but in my experience I more often see the moving blob, than the immobile one.
Part of the problem might be that I didn't focus enough on haste. I gemmed for Resil/MP5, but I could swap those out for Haste/MP5 or Haste/SP. My FoL heals are about 1.4 seconds now, and my HL heals are 2.2 seconds. But with a change in gems I could get much closer to my PVE cast times than I am now. That would certainly help with the interrupt situation and allow me greater healing throughput when I am standing still. I might try Haste/SP and see how it goes throughout the rest of the week.