It's disappointing, but it would have been tolerable had the ME2 characters not all been reduced to one-note caricatures of themselves. Mordin, often held up as the best example of how BioWare handled ME2 characters, gets reduced to the atoning-scientist archetype, losing a lot of the aspects that made him so unique in the first place, and Legion is really Legion-in-name-only.
Then again, the same can be said for most of the ME1 characters as well (the only real exception I can think of is Tali, but she's one of the sole characters that benefits from having the same writer through all three games). It's just more pronounced with the ME2 ones because they barely get any screen time as it is.
I understand that BioWare was pressed for time, but it's almost like they didn't even know their own characters.
Oh well, it is what it is. Better to have them all die off in the Suicide Mission, I guess.