No, they're fine. I eat them alive with my powertech, sniper, and juggernaut; focus them down. Interrupt their lightning. The bubble doesn't absorb THAT much damage, and casting it leaves a debuff timeframe which leaves the Sorc/Sage very vulnerable; a good sorc/sage will DOT and LOS and heal up, but without cover and with more than one enemy on your arse, you're done.
The argument comes remains that they have a LOT of CC, which they do; also, a lot of sorcs = a lot of damage and CC, which lends to the misconception that they're overpowered. But how is that any different from having, say, 4 snipers in the group, spamming Ambush, or four mercs spamming tracer missile, or four powertechs spamming rail shot?
They're fun and appealing classes which garner high numbers. We'd be hearing the same arguments about snipers/hunslingers if they were as numerous as sorcs/sages.