But necro's used to be meta in TA and RA and [Glad] used to play them in split ( a long long time ago and many skill updates later), so I wouldn't say they are bad in skirmishing.
Necros just match up horribly against eles after the update, also TA and RA are different since it is 4v4, eles are better in most 1v1 or 2v2 scenarios.
Who says you will have to play 7 casters (with survivor armor)? There could be other options as playing it in a heavy melee build or an energy drain build. Guess you could even make a degen build with not too many casters.
I was under impression of a hexway. People have played builds with hexers augmented by other damage dealers and it could be possible, but only good in very specific metas/fluxes in specific matchups (migraine for example).
So... In which situations would it be possible to play a curse necro?
Sadly probably none, unless people are playing 3-4 fronts/melees again. Mesmer/Ele is just in a much better spot in the current interation of the game. The only reason people run SoS necro is because 1. It runs flags well 2. It is provides midline dps/degen while being almost impossible to shutdown by wastrels and 3. It synergizes well with other forms of degen/shutdown (ranger/derv/fire ele/pblock).
Conclusion: The biggest reason that hexers (mainly necros) are bad is because they do so poorly against eles/wastrels mesmers which are both huge parts of the current meta. You can either design a build that is strong 8v8 or strong in straight up 4/4 or 5/3 split. Unfortunately gvg is very dynamic and it is almost impossible to create a necro bar that is strong in 1v1 and 2v2, and strong in 8v8, while it is very easy to create such a bar for eles (see mind shock/mindburn/lsurge). Necros (or degen chars in general) are very poor offensive splitters since they lack the burst killing ability to pick off people/npcs faster than your opponent can respond. They can be good defensive splitters, but defensive splitting is useless you have a win condition (either at 28 or through killing main), which hex heavy builds lack (since it is too hard to kill main if you split your dmg up) and you have obvious difficulties at 28.