Hello there! It's UP for me because it really is a good game.
But while damage and defense multiplier is good for most games it's more like a waste of time in this one. As an active player at level 47 I can tell that what should be more focused on would be free purchase for Ultracubes (paid content for lots of things like unique skins and currency as in Hypercubes) or infinite Hypercubes (the blue cubes which has lots of uses like buying stamina for battles to getting characters).
If such can not be achieved I believe that infine Stamina will do WONDERS for players, much more than simple multipliers because as long as you progress enough with the basic levels you'll Unlock the RUST map stage where you can obtain Discoins and Mania Essence (that you need for leveling characters till you reach phase limit), skill modules (needed for upgrading skills), Fluids and items needed to phase UP a character(which can be obtained in stage battles in the Rust or normal campaing as the characters have 3 phases you will have to get them). And before you ask, as you level UP you'll unlock superior stages to get better items, Discoins and Essence which cost more Stamina per fight. But there's the Raid and Multiple Raid system which means that you will only need to fight normaly only ONCE, then you just can Raid(instantaneous battle with %100 win rate) as much as you want(as long as you have enough stamina that is).
Thank you for your pacience.