I totally agree with the fact that this game demands way too much time for what it gives. I enjoy fighting challenging battles: Arena, Raid, Events, period. I enjoy (slowly) collecting and developing characters, so I don't mind the lottery-style grind. The rest is just forcing me to waste time and slowly pushes me away of playing this game. More precisely, they should:
1) Make GW a weekly thing, not daily
2) Remove challenges altogether: they have exactly no interest/fun at all. It's 100% a chore (even if an easy one)
3) Rebalance the grind a bit... although since this is mostly a collecting game, we have to have something to collect, so I don't mind that it's slow. At least, simming battles doesn't take long.
4) Move Arena payout to be a daily average instead of a precise time of the day