Laezel's "doubts" are whether the Githyanki are evil and bigoted enough for her tastes. Shadowheart shares her hatred of ever telling the truth even in circumstances it's of benefit to her, her dedication to an evil god and not much else. Other than being condescending and hypocritical Gale doesn't really have any characterisation at all.
I think it's entirely plausible all three of Laezel, Astarion and Shadowheart are on redemptive paths, probably alongside Wynn and Gale and I half suspect Karlach too. But that's not enough for it to make sense anyone would ally with them, nor does the trajectory of those arcs look on course to be worth the trouble until Baldurs Gate 4. The first chapter represents about thirty to forty percent of the game so hints that they may start considering change towards the end of that chapter doesn't leave much space for a good redemption. It's similar to taking Viconia as a companion in BG1 with expectation she'll eventually stop complaining about you doing good.
