Tuvix was an entire species, the only member of his race. A complete civilization.
To balance the scales against all the Talaxian/Vulcans hybrids in the universe you would have to put all the Talaxians or all the Vulcans, or even all the humans in the universe on the other end of the counter balance.
The needs of an entire civilization vs the needs of a couple selfish assholes.
The needs of the many outwigh the needs of the few.