Crazy thing and I have been researching this. I hope to have an upload sometime to show it. Some background on what all I have been doing. I started with a titan got him to level 15 and swapped to the defender subclass. No issue with learning the new defender skills. When I made a hunter I started him with Blade Dancer (not gunslinger). After maxing out the Blade Dancer I swapped to gunslinger. After a few upgrades/levels to the sub class I noticed all the base skills were basically grayed out even though they have the green circle full around them. This implies I "should" be able to learn the skill but it has not allowed me to yet. I cannot doublejump, throw grenades, or even super/melee which is very lame and IMO is a possible bug to this class. I don't know if it has something to do with starting off as a blade dancer but I am curious to know if anyone else has experience this type of issue.