Flap62: Possibly for the same reasons (or lack of!) that everyone went crazy for VG a couple of generations ago? Conceptually valid but with not much payback in the real world? Indeed, wasn't the initial thrust (pun fully intended!) behind TVC (at least in the west) aimed at giving the pointy stuff better STOL characteristics?
Eclectic: Rather less stealthy when applied to a big, honking legacy design like Su - 27/30/35 series, surely? And with IRST as it is today, spreading the thermal footprint everywhich way can't be a good thing, can it? As for increasing speed and engine life - how?? I'm just seeing extra weight and complexity.
I do see less reliance on control surfaces and better low speed authority as others have stated but at a cost (the aforementioned weight and complexity) but I'm still not seeing how, in an operational sense, that might lead to fewer Su - 35 shaped smoking holes in the ground.
Regards,
Frank