I was speaking generally not specifically for this list.

My beef with Vader is that he is SOOO specific that his use becomes to narrow, basically you spend 36 points to decrease your chance of rolling bad against ships.

Tarkin for a similar price can do literally anything. Want your squadron game improved? Suedo expanded hangers for ALL your Ships. Want to be harder kill? Suedo Redundent shields for ALL your Ships. Want to be hypermanuverable? He can change the speed of your Ships by 2. Need a little more damage? Add CF tokens. And the best part is I can change from turn to turn!

Leading shots screed and OE also work against squadrons so when you HAVE to get that last bit of damage through on Jan or your ship is going to be shredded by yavaris b-wings you can. Vader can't.

Generally he can increase a roll by 1 or 2, rarely does he do more and often his reroll is just as bad as before.

With devastator he is probably a "better" pick but I am still disappointed in him...

Pretty much all of this. And then compound that he ALSO costs defense tokens. Super expensive for what he does in FP and in use cases. Even for devastator, I don't NEED any help getting rid of def tokens, my opponent can do that. If they are afraid to shoot at the ISD because they havent thought it through and are afraid I will get more dice, GREAT! it's still a frikken ISD!