The only problems you may face with some sets is that you either can't lock down enough mobs (Gravity in particular) or you don't have many AoE attack options. I'd also shy away from using the AoE immob - especially at low levels. They do nothing for damage mitigation and on teams it just makes them attack you back.
I have six dominators (one for each control primary and coupled up with the thematically appealing secondary), one at lvl 40, another at lvl 34, three between lvl 22 and 28 and one below lvl 10. My earth/earth dom is level 34 and it's really fun. Earth assault may not be the best looking thing on paper but when you run around clobbering things with stone mallets and the screen shakes you just can't help but grin manically. The only doms I can't get into are my fire/fire and ice/ice. I just can't seem to solo with my fire/fire and I've just got a lvl 32 ice controller so I'm a bit bored of ice/ice right now.
So yeah, they're only really squishy when you can't mitigate the damage well enough but at that point in the game most archetypes are squishy anyway. I regularly become the tank with my plant/thorns so it's very possible to not be squishy with a dom. I like to think of Doms as blasters who forgo some ranged attacks for more advanced control options, so if you're good at blaster active defense then the Dom version should be easier.