Firstly, I am by no means a Krieg master. I he’s my second or third most played, but I’m definitely not as much of an authority as any of the other posters here.
Second, I don’t know if anybody actually uses StV without the COM boost. At least from what I 've read, the very general consensus seems to be to not take the skill unless you can fill it to 10/5 since 500% damage is a better proposition than 250% for the same self harm chance. And at least in Mania+Bloodlust builds, people take buzzaxe bombadier for the extra explosive boost, and that u helps close the gap. I’m not too positive with how it works in Mania+hellborn setups though.
There is also the fact that those 5 points can’t really go anywhere else. FtR is useless with RtB, TotK is also fairly counterproductive to RtB, so what else can you do with those points to progress down the tree? There isn’t really any other skill that can give you as much as StV, at least if you’re going melee.

