Which sucks... Bosch water pumps or my belt tension?

90 740Ti.
I replaced the factory water pump with a new bosch unit - eight months later, it was leaking quite a bit from the weep hole.
I replaced that bad one with a factory replacement (free).
Now I can find coolant along the water pump fins. (AKA, same leak as before.)

Am I doing something wrong, like weird belt tension, or do the bosch pumps suck? I mean, I can keep getting free new water pumps, but this is RIDICULOUS. I haven't had one last two years yet.
I do notice that my alternator belt bounces, despite it being rebuilt and having its bearings replaced, might that contribute?

I do drive pretty hard sometimes, but I don't know if the bosch seals are not up to it, or it's unrelated.

If not, I guess I'm going with the hepu unit. Does anyone have any advice on this?

I'm getting VERY annoyed with constant problems with my cooling system.

Thanks,
Will
--
1990 740 Turbo, on its way to stock specs, maybe beyond