That's true about starters but lefties get that advantage either way. It doesn't matter if they're split up or in a row. Yes, bunching them together might impact run-scoring a bit but I was thinking of individual OPS performance, which it won't affect. As for leads/deficits late in games, I suspect the lead/deficit would have to be pretty substantial for a manager not to say "aw hell, three lefties are coming in a row, I'm just going to throw a lefty out there to make sure nothing bad happens". Every pen has one lefty reliever and lots have two of them. Chances are, one of them isn't amazing so why not put him out there to face a trio of LHB?