I agree with Johnny, the $50 spender (give or take) is the sweet spot for game enjoyment. The p2w spend hundreds or thousands to get everything maxed out right now, and conquer all of the content at light speed. That plan succeeds, then they become bored. The f2p will double their progress for well under $100, if they do it early.
As far as an additional challenge, HC had the Grand Arena, where you use three teams, and have to win 2 out of 3. Top players can hide between 1 and 3 of their teams depending on rank. You need to have a large bench, or at least 2 good teams and guess if their hidden team is op or cannon fodder, and match up accordingly. That was the most challenging part of the game for me. We should have a GA here as well.
