I don't personally think arena or the shards are broken. I think the best player should stand on top of the mountain until he is removed. Players should not be able to weaken their arena squad to let others get first place when they didn't buy it nor earn it. Arena ranks should be more reflective of player growth and skill. Here are two simple recommendations which do not change the current arena environment nor take aim at the communities built at the top of the arena.
1. 24-Hour Arena Team Lock-In: Easy enough, have a separate interface where you put in "tomorrow's" team you want to run with. The team is live, so any upgrades to mods or gear will apply, you just can't change your team. Newly unlocked characters will have to wait 24 hours.
2. 10 Attempts: You get 10 attempts daily. You cannot buy more attempts. 10 gives all players enough leeway to drop a couple of attacks or defends. The spending will come from people "needing" to better their team to get a decent rank.
There are always unforeseen consequences to changing anything. But I thought this was a fair way to do arena. And I would definitely not benefit from these changes.