Invader set for Witch Elf

[Sulorie]

You are not half dead, if doing pve instances. Maxing aa dmg gives you a lot more sustained damage.
Not every set has to be a straight upgrade for every situation.
Invader is not good for WE but it doesn't have to be either. Imagine you enter t4 and start to earn sov crests en mass, you would skip all other sets and directly swap to sov. This is not intended. Some sets are just filler.

Earn Royal Crests en mass? You need rr 70+ to equip sovereign. You need to equip full invader before you get Royal Crests in your zone bags. I dont see your point. Why would invader on intention be inferior to vanquisher? Then whats the bloody point? ANd how does it make sense that it requires higher renown rank to wear?

It's a roadblock and an alternative set, it doesn't have to be the set you want. It slows down your progression towards sov set. If you could farm sov set the moment you enter t4, people would do it. Obviously it is not possible, so people have to unlock certain sets before being able to gain and wear sov items.
There are more cases, where sets are worse than the previous sets, like duelist/deva and anni/merc. The last ones have a lot worse set bonus compared to previous one for some classes. For this reason people tend to mix sets.