It might be newbie-friendly to not have all things unlocked from the beginning; it’s easy to get scared away by the huge amount of options. But I do not think that it should require a lot to unlock something, and once you have it should probably stay unlocked on all characters. Also, skill points don’t seem like the best currency to use for this, since that would mean not unlocking something in PvE instead
I’m playing a guardian and I have a elite skill that makes me invulnerable. In S PvP (haven’t tried in any other game mode) it happens a lot that when I’m escaping I turn it on, a couple of “Invulnerable” sign appear but then I get downed, before the invulnerability has ended. It happens that I have the same problem while using skills that block all incoming attacks, but that might be due to condition damage so I can’t guarantee that that is also an bug.