I put the first part only, because the whole raid takes > 2 hours (Necromancer's Gate skraid)
It is Necro, the easiest skraid (with Amon Sûl, also soloable, but we must protect the NPC Candaith, more chances to fail...),
but I think it is not normal that a 12-man instance can be done alone !
I'm not top geared and I did not use my tank gear (I must use it in WP T2C for example, otherwise the last fight is too hard)
The huge speed debuff of last Lieutenant (Shepherd of Filth) was very annoying (I cannot interrupt it), but his DPS is really low.
Some parts were more difficult when I got 2 LTs at same time + mobs, if one of them was the "Brothers of Destruction", who seems to be the strongest LT, when we are alone, but I just added more vitality.
Wardens can certainly do it even more easily.