This is what I see being the biggest issue with the Arena right now, you can either choose to play the Arena, or play the rest of the game.  You can't do both at the same time or it really screws you in match making as you collect champions and build up teams for CB, faction wars, doom tower, etc.

Apparently the current strategy for the game is you need to build up warmaiden/starter champ/high katune/apoth and just play the arena for 2 years to max your great hall and then focus on the rest of the game.  I had the same arena team for awhile and it was very effective, but it stopped working once I improved other areas of the game.  Turns out player power is a curse.

Forcing PVP is a horrible idea for any game imo.  Arena almost turned me off at day 2, but I stuck with the game because it was doable at the time even if it was miserable for me.