I think some of these things might have been already discussed around here, but this is my turn.
So first give better rewards, arena-rewards are nothing compared to PvP-rewards for highlevel players. After 8 wins we should get something like:
More gold, like 5000
Some glory, like 20
10 or 15 trophies
1 runic traitstone
And so right now traits are disabled in arena.
They should make it optional to turn them on/off.
On so the higher level players can actually enjoy their traited troops they never use anyway.
Off for either the players who like it this way, and for the lower level players, so they can have a fair fight.