Don't get me wrong: Tasha's death wasn't devoid of impact, I think the event of it was handled well, I thought they did a good job of that given the time they had to work with. Its more like I felt the exact moment was kind of... ehhh... what's the word? Abrupt? Which, in hindsight, suited her, she wasn't the kind to die slowly and if anything tried to kill her slow I'd feel damned sorry for it.
I can also see how that could be considered the final last humanising act, the will to sacrifice himself for the good of everyone with no hope of survival demonstrating a level of humanity that most humans are lacking. The thing was I think that even that revelation was blunted by the presence of B4. B4's presence is only understandable if they intend to do another movie and didn't feel confident that they could create as strong a story without Data, which to be fair they may be right given how all the TNG movies at some point or another have hinged on Data's presence and the particulars of his character.