Changes in the catalyst arenas
The catalyst arenas have not been modified fir a while, whereas the players needs have evolved. Veteran players need more T2AC and T5BC to improve their numerous 5* (that ate the standard).
To add milestones with T2AC and T5BC shards would be an easy and cheap change.
By the way rank rewards are weak, so why not to allow 6* to reach the last milestones quicker ?
I know few players that still play these arenas (average veteran players get the content in other ways). And no one try to get a rank reward.
I play them often and each time I have the feeling to loose my time.