My bassist plays with 2 fingers, and he does alright. But he's not playing Digiorgio speeds. And we aren't necessarily Tech Death. We're more Old School Death Metal. But we take influence from Prog and Tech by having fretless bass and some crazy drum parts. I'd say it depends on what kind of Tech Death. I think it's possible to play Obscura's music with 2 fingers. Necrophagist is a maybe, but all of the tapping make it seem hard. The stuff Steve does on Human or ITP? No way, some of that stuff seems to REQUIRE 3 fingers. It's possible to play Tech Death with 1 finger, but only if it's really simple on the bass.
Bottom line, it's all about perspective - how crazy do you want your bass parts to be? I personally care more for my bassist to have more work with the left hand than the right.