There is a large increase in difficulty between each tower league. It isn't something that I seem to be able to buy my way out of. Going from rank 4 to rank 3 I can kill just about anyone I've seen in two hits but possess about 10k to little health to survive the first hit from an opponent. The only answer is to slowly grind out enough health to tank that first hit or enough power to one shot most opponents. Looking over the forums this is intentional design and most tower levels have a similar increase in difficulty. So to avoid going through several rank up or down screens between each battle as well as sitting through losing fights the solution most players have is to refresh several times. Why not use this as an opportunity to sell a conveniece? Perhaps for an amount of gems a player can be sent down a level. Or pay to toggle off the rank increase for a week.