I have had Ima on my first account. I farmed him on nodes to 5th star for Yoda event and used as leader for 4 jedi team. It was amazing to see 4 counters or response on AoE atack , but it was rare.
Now I am using new account and I will not farm him again from the shop. Maybe if you have all the best jedi in the game, his lead will work , but do not wait for super results. Arena will have sense only if you find tank team with Opress, Fives , Phasma, Kylo ... Only long fight can bebefit counter Ima. The glass cannons with tank is very bad opponet for Ima's team because of its short time of fight.