The point was not using spinthrust against a facehugger 1vs1 but against someone at optimum range. I did this often enough, taking one or two down from a triple gang on me with only a lance. Fake attack at one turn it into the other guy who stops blocking. And then I died as the last one spammed me.
The point being if you have one pikeman in a group and fight someone else you always have to expect getting that pike into the side. So the pikeman destroys melee capability of all enemies in his range. The pike (and similar weapons) are good enough for this already, just look at how many kills a good pikeman can get, and that's discounting all the guys that died because they downblocked the pike only to be sideslashed. A longer weapon (I don't know how you get 55 I read 350 in OP) just means he can endanger more while being perfectly save. If Marathon is actually right about the hitboxes wouldn't this also mean that he can thrust directly through his teammates with no risk of teamhurt?
The other thing is that "this weapon is useless when they get close" is not really a problem. My bow has speed 50, can't block or even chamber, heck I get staggered when they touch me, but I kill people from facehug range all the time. It's not like you can't carry a secondary weapon.