Pre-pull regen?

[EaMett]

Personally, I tank (PLD) most of the 4 man content because it makes for shorter queues. Ex roulette is the only one I heal because I like to get through them quickly and fast paced tanks are easier to find than healers who dps hard.

Regen mid pull is absolutely fine (pre pull doesn't really make sense or line up right with your other skills). Just if, for whatever reason, the tank misses a mob, bring it back to him (don't stand 50 yalms away). Even better is to run along side them.

The only times you want to refrain from doing so is if your tank is finding it hard to grab aggro because of it. Either they aren't comfortable with their class, have bad latency, are low on mana, are warriors (the conal does make it harder), or simply dislike it.
Literally takes two pulls to get an idea of the situation and adjust.

Regen mid pull is an extra dps uptime of a few GCDs as it aligns perfectly with your other skills, keeping you from having to tetra/bene/cure early in the pull (or sometimes even at all).
It's way more wasteful to use an ogcd while or at the end of running and then use a GCD on regen once you arrive at your destination. (Or even worse, use a gcd after running)

When you factor in the fact that most of the time it makes perfect sense on large pulls for the tanks to free up as much healer dps as possible (holy is unrivaled). Making your life as a healer easier should be the default. Only cast it aside if your tank is having trouble.
(And make sure you make it up to them on bosses since it should be your job to make sure they never use tank stance )