What to do next?

Rap027

This is my current 4* and one 5 * roster (i have maxed 3 stars but who cares). I am level 44, free to play, and have finished act 4 but not started act 5. I just opened my first 5* last night and got taskmaster who i hear is only good awakened and with synergies and i don't have either of those. It will take me awhile to get my next 5 * (i only have 80 shards left). I want to focus on building a 5* roster to look towards the future, but I also have some good 4*s. I don't get many t4ccs so i can't r5 anyone right now (or r3 taskmaster when i get him there), but what should my focus be? I love warlock, not great with ghost, and know nothing about taskmaster. Should I save up and focus on 5*s or max a 4*?

Next and bigger question---what should i be using my stamina on? Should i try act 5/uncollected? should i spend forever fully exploring act 4? Event Quests have always been my focus but apart from those. When should i try ROL? Anything i'm forgetting?

Thank you all for your input.