Actually we haven't a fucking clue what they really look like, according to the bachelor party on illium.
They could be pure energy, as nothing in any information about them or any of their character interactions indicates they even have biology. The tentacles are the only constant, and those are all nearly identical.
Then you have Samara's loyalty mission, which always ends with "unable to recover mutant asari." Which is either a "lol not really daed" or more consistently, evidence that they simply don't exist as flesh and blood.
Actually, judging from li'ara's random dramatic character shift, initial encounter (accidentally hit the wrong button my black ass) and the asari presence on the citadel before anyone else, I'm going to go ahead and call it that the asari are agents of the reapers. They watched the Prothean's die and the only reason saren was always one step ahead of you in me1 was li'ara was feeding sovereign (or... nazeera...) every bit of information you uncovered. The only concrete contradiction to this would be vigil not going all invasion of the body snatchers on li'ara, but that can be explained away pretty easy. Not to mention how quickly the whole "reaper" thing was covered up (if they can control your mind one way, they can control it other ways), the collectors always seeming to know the position of the Normandy...