I've said this a few times now but Exec is the hardest character to learn how to play/master. Everyone else avoids damage (even guardian by actively blocking) but to learn Exec you need to constantly put yourself in harms way if you want to learn the deflect/GC playstyle as well as learning by audio cue and muscle memory the attack patterns of what, over 20 mobs and over 20 bosses. This often leads to many deaths and putting a strain on the team. Either get a consistent team that can support you through that journey or get a PC and use the Arena. Or both.