But the better one is still 8%.
If a 4* hero have 200 DoT damage and 800 HP before LB and a 5* hero have 300 DoT damage and 1000 HP before LB, 4* get 8% increase in attack and HP while 5* get 7% increase in attack and HP, which one get more benefit from LB?
Lets do the math:
4*
DoT damage increase = 8% × 200 = 16
HP increase = 8% × 800 = 64
5*
DoT damage increase = 7% × 300 = 21
HP increase = 7% × 1000 = 70
16 < 21
64 < 70
So 4* increase is smaller than 5* increase, does this mean 5* get more benefit?
WRONG
Those numbers is only on face value, we have to put it into simulated battle calculation:
Before LB:
4* DoT against 5* HP: 200 / 1000 = 20% HP taken
5* DoT against 4* HP: 300 / 800 = 37.5% HP taken
After LB:
4* DoT against 5* HP: 216 / 1070 = 20.19% HP taken
5* DoT against 4* HP: 321 / 864 = 37.15% HP taken
So after LB, 4* damage actually take more portion of 5* HP (increase from 20% to 20.19%) while 5* damage take less portion of 4* HP (decrease from 37.5% to 37.15%).
It means 4* get more benefit.