I think I'd go DK. just seems to be in a better spot right now for what you want to do, easy major mending and lots of group utility.

Also better options if you decide you want to do something other than heal, and it looks like strife is getting a big cost increase next patch which would hurt the NB healer a lot.

NB tanks are incredibly powerful right now, besides the utility of a shield and damage buff (which a dk dps or healer can provide, and NBs provide a major protection aoe buff that's a bit stronger + better ult management), I'd say they're equivalent in a lot of ways. I haven't heard a lot of hard evidence otherwise.

As for healer, yeah the strife nerf hurt, but NB healers literally never ran into mana issues to begin with, that's why the nerf happened. My healer runs Julianos/Willpower right now because of the lack of spc/worm cult pieces I have, she has 43k magicka and her combat prayer burst heals for 13k. With siphoning attacks she never runs out of resources, and strife cost so little that it was very easy to weave. You only need to cast the ability once every 5 seconds anyways (I'm not sure if multiple casts means the healing applies to a different person each time, I haven't tested that). Also, considering how easy it is to set up DoTs for healing on a NB, you can weave heavies to get major mending on them. They're very fun and very effective. But I definitely would not stick it in a trial unless you had a templar tank/dps/2nd healer running shards for stamina players. NB doesn't provide resource management for other players, they support best by getting the PVP ultimates, warhorn/barrier, or using veil of blades to buff up their team while doing decent dps throughout. I've never really tested it in a vet trial yet because I'm afraid to and players don't recommend it, but when I get the chance I'll get their feedback. In the meantime though, they can run basically any vet dungeon effectively even with just purple gear.

Healer's Habit, SPC, Worm Cult are all good. If you can somehow fit a monster set in your build (such as going a master resto staff/willpower), then I'd personally run Sentinal of Rkuthamz, because it gives a lot of stamina regen in an aoe. Useful to keep your team's dps up.