I hate it. XD I like the idea of getting rid of useless cobalts for something better, but DAMN… they are freakin’ expensive on their own.
Trade 3-for-1 is an insane kick in the teeth for anyone who’s bought them with real money. Not sure why they put “beta” on the feature too - because the game itself was still beta, the last time I checked
lol.
Honestly, I would encourage anyone who doesn’t like the feature, to NOT use it, and post constructive suggestions for alternate options.
I personally wouldn’t mind something like 1 “desired tier card” + 3 “tier below cards” = 1 new “desired tier” card, and which ever “desired tier” card you use, depends on the merc you get (ie. if you use Sparks, you get Sparks. If you use Vassili, you get Vassili, etc.) So there’s still a card “cost” for it, and perhaps something like a 10,000 credit cost would be MUCH nicer than the ludicrous 24,000… I just think a re-roll would be better than a “trade in”. 
Just my thoughts.