It only makes sense that they would be more useful in groups because you typically have someone holding the enemy's attention so that they do not move around which is slightly important when trying to get to a specific position. This is also a multiplayer game so it stands to reason that stuff will cater towards it. You will still kill things perfectly fine even without getting all your bonuses.

Is it really that hard to understand that some skills will just work better in groups, just like some skills work better solo? Why the hell would I use Medica on Conjurer when soloing, for example. Why would LNC use Keen Flurry or PGL use Featherfoot if they don't have to take damage for extended periods of time when they have a tank?

PGL has a combo that does not require positioning to do full damage, just for crit bonuses (and after the first enemy you can take advantage of it by initiating on the flank or rear on the next enemy) and LNC only requires Heavy Thrust and the initial hit of a combo to land for the bonus to work, which means you can just open with heavy thrust from the flank then Leg Sweep and begin your combo without issue.