ISO flow rate is not the problem most people have. The actual issue is the cost to level a 4* from 70 to 270 is astronomical.
Awhile back, they lowered the cost to level 2* and 3* characters, but they didn’t change 4* costs because there were only a handful of them.
Consider total cost to level a character from first cover to 13th:
1* 28,420 (for 3 cover characters)
2* 69,529
3* 119,919
4* 365,896
5* 551,296
Now look at the following ratios between tiers:
1/2 28,420/69,529 = 40%
Meaning, you need 2.5x the amount of ISO to level a 2* compared to a 1*.
2/3 60%
3/4 32.7%
4/5 66.4%
Using this comparison, it’s obvious there’s a staggering amount of ISO needed to level a 4* relative to the 3* tier that most of the ISO rewards were designed around.
If they brought the 3/4 ratio up to 50%, we’d be looking at full level cost of roughly 240k.
If they brought that number to 60% like the other ratios, we’d need just under 200k to max level a 4*.
200-240k ISO should only take a couple weeks to make for most 3*/4* rosters that play pve and pvp.
This change would at least allow players the ability to keep up with new character release schedule and puts the onus on the player to find covers.
From the developer stand point, no need to worry about adjusting ISO rates for rewards or ISO sales values for covers.