As the support role, lightning provides arguably the most benefit to any group, by helping set enemy off balance, which = more group damage.

There could be situations where a group has other lightning staff users and/or Sorcs, so have this covered, in which case there would be nothing wrong with a healer running flame staff and arguably they should, as this can potentially increase their damage contribution.

I guess there is a shout now for ice staff since its been changed, as it provides some group support, but Ive not seen it or used it so I have no idea how significant these are yet.

I generally use lightning.

But on a warden I tend to go Birds/Insects for off-balance and vulnerability, so the debuff point of lightning is lost. On the other hand, a lot of the DPS that I find time to bother with is Shalks, Orb and an ultimate, so lightning isn't a bad DPS choice, so I haven't rushed to deploy alternate gear.

But mainly, I haven't bothered shifting my gear to be more optimal, because I'm not grouping that much these days, and what used to be best is still close enough.

Lightning staff for pve, s+b in pvp.

Lightning staff will remain meta for a long time apparently as it provides offbalance and minor vulnerability (even if this debuff has become pretty common amongst regular skills nowadays).

Frost staff would of been a strong contender with the introduction of minor brittle.. however, minor brittle is only applied if you are holding a frost staff and if you proc chilled.. both of which kinda work against the healer.

Since wall of elements is probably the only ice skill you will use, the chances of it proccing chilled is 2% per tick which is not enough to rely on. Like a lightning staff, you would probably want to use an infused frost enchantment to get a 40% chance every 2s to proc chilled or 84% with a charged front bar resto staff...

However however, unlike the lightning staff which will proc off balance to concussed enemies that your team can make concussed for you lowering some of the pressure from the healer, with frost staves you are the ONLY person who can proc minor brittle with the staff active on your bar. This absolutely forces you to use an infused frost enchantment with charged front bar, no question about it. Immobilize and minor maim is most likely covered by your tank. The shield it gives is only applicable to ranged attacks, nice, but not completely necessary.

As a result, Frost staves appear to be best placed on a Warden DPS that doesn't need to sacrifice much to proc chilled since Winters Revenge has such a high innate aoe proc chance (in my tests, about 15-20% without charged), they already want to proc chilled for their personal 10% crit damage passive, they get +10% frost damage and their skills are a decent mix of aoe vs single target making fire staves not as important to their dps. There also one of the lowest mag dps right now, so it's not like they're sacrificing a lot without a fire staff to begin with.

I imagine a bunch of healers are using frost staves now thinking they're providing a nice damage shield to everything and a nice damage boost via minor brittle, but not realizing how ineffective it is without the proper setup. Stick to lightning staff since it's one of the only good pve options for off balance and you're most likely using a resto staff front bar anyway.