Well, I mean mostly if they go after the 0 CD and remove that, then the entire build just falls apart. As long as it has the 0 CD I think it will be fine.
The problem with Doppel C2 is that the new skills are limited to 2H Swords only and if you swap to that from a spear, then you are going to lose the Finestra buff. Sure, you could get Cyclone and Deeds of Valor level 10 only, which is also a pretty good option, but I feel it would kind of be a waste to not take full advantage of everything that class can give you.
By big players I do mean Doppel C2, Corsair C2 and Fencer builds.
Let’s say that you do instead take Hoplite C2 for something else to deal more damage, then you would still not have Peltasta while those other builds will have it.
Even though at Rank 7 there will be stronger builds, it doesn’t mean that this build would be that far behind, I think it is fine as long as the 0 CD on Sky Liner is a thing. If I had to put it on a “Tier” on my list, it would be “Tier 2” (second best tier), at Rank 7. Maybe lower at “Tier 3”, since we don’t exactly know what level 200+ looks like, if Peltasta becomes even more important (lots of grinding), then it certainly would go down.
This is why I prefer to wait until the balance changes calm down before start planning on any builds for Rank 7+. Look at kobt, there is a maintenance almost every day and lots of changes going on around, I am sure there are going to be more changes once people reach Rank 7 and start playing around with the new classes.
They could nerf Sky Liner, or they could remove the Doppel C2 skills restriction of 2H Swords, or any other change.