I'm curious as to why you would rule out the Lore-master because of its squishiness when the Rune-keeper is just as squishy, doesn't have a 'real' pet and, honestly, probably has less survivability unless you sacrifice your DPS.
Anyway, between the RK and Warden, that's tough. I've heard from tanking Wardens that they aren't quite as good as, say, a Guardian in that area but supposedly their DPS is somewhat better than it was before. RKs have gone through some mechanics changes but, from what I've played, they're in a good spot DPS-wise. Can't comment on their healing ability just yet.
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