If you save them, they become a war asset in part 3 and keep their word, helping in the fight against the Reapers (provided you spare the queen twice.) Imo, that was the wrong move. It was the Paragon decision, but all too often, the Paragon decision was rewarded, at least 99% of the time.
"No good deed goes unpunished."
That was as good as any opportunity to put that into practice. Yeah, they give a little pause in ME3 once the Reapers manipulate them again, giving you another chance to doubt your decision, but they should have been treacherous from the jump. The first conversation with the possessed asari made my skin crawl. Any fool dumb enough to trust that deserves that knife in the back.