Ya I like Xerath and Brand but even with the changes current support doesn't lend itself to you finishing Rabadon's in any time close to playing a mid. Which I think is kind of mandatory to carry a game as mage.
In the 40min game, of course I'll get it and be able to pull a win out.
Xerath would be my go to but I was thinking Blitzcrank. The thing is, if you find someone to duo queue with (me playing Blitz) they seem to stack the low performers who typically get carried onto your team. The worst people I've ever had on my team have been when I duo queued, like shockingly bad even in gold+. I can see why they'd make that a thing, and there was even official confirmation they were doing it.
I just don't think playing your promos as support then trying to get into plat as support is a good idea at all.