wow u really impress me. may I know what heroes (and their levels) you are currently using for arena?
As of now, I have 4 legendaries except TG and Champion and all my others are 90~108 except my Ninja which is prob 88 atm. From my experience, best way to get up the rank is not to "save" your HB. My initial thought was "why would I spend 20,00 HB on some hero other than a legendary." I realized that this is a wrong approach. My Druid ended up being very high (100) while my other heroes were in 60s. So I couldn't move up in the arena because 100 Druid doesn't do much when all other heroes are low lvled. So my suggestion is lvl up heroes evenly instead of one being so high. Also make sure you as much as battle chances possible.
*In the arena I usually go for DPS battle with Ninja and Assassin.
there's always the shards option anyway. I have enough for a pally right now but I already have one and i'm saving for a druid.
Just can't imagine weeks/months from now when I finally get reallllllllllllllllllly bored of this game and uninstall it. All that time wasted lol.