I decided on my ALT account that has weaker units to just run PRO all day long. Even with Lightning friend, because in order to solo ELT, Lightning should be 500+ attack and have Diabolos Man-Eater. I never lose when farming PRO.
The plan currently is to get the sword, shield, 2/3 of the tickets, SQ, and as many 6* mats for Lightning as possible. Not sure I will be able to complete the mats, but I will have a jump on the next event and its mats, so I can level her and any other lucky 6* at that time. By then, the account should be in a lot more solid footing with units. I was having trouble keeping up with the ALT account, but by the end of the event it should easily be rank 40+ because of the awesome rank experience. The really painful part is going after the trophies again. Don't quite have everything for farming HR yet, but I'm close
My primary is easy to run - I just check it every four hours or so, run ELT, run the Colosseum, and then let it recharge. Only time-waster is doing dailies for both accounts early in the morning.