Ermmm...
Yes it's only a 212+, not a 212 Evo, but it shouldn't make that much difference should it? The 212 coolers are better than the stock coolers...normally...
The cooler base shouldn't have warped and yes, you'd see if there was a bad contact from the thermal paste residue.
It's still running warm, but that's not what I expected to see when you replaced with the stock cooler.