For what it's worth, Earth Bull combos with both WD and MB versus a Pegasus attack combo:
Defense types always launched first
BB-10 stadium
MF Pegasus 145 RF vs. MF-H Earth Bull GB145 MB
Earth Bull: 6 wins
Pegasus: 4 wins
2 instances of pegasus being KO'd
MF Pegasus 145 RF vs. MF-H Earth Bull GB145 WD
Earth Bull: 4 wins
Pegasus: 6 wins
0 instances of pegasus being KO'd
Only 10 rounds each, so it's not conclusive. For example, there were instances of MB being knocked into the wall, whereas it would have been a KO if there had been a pocket. I would guess that if more tests were done the results would be even closer. Anyway, I saw no significant balance issues with MB. MB and WD behaved very similarly.
Defense types always launched first
BB-10 stadium
MF Pegasus 145 RF vs. MF-H Earth Bull GB145 MB
Earth Bull: 6 wins
Pegasus: 4 wins
2 instances of pegasus being KO'd
MF Pegasus 145 RF vs. MF-H Earth Bull GB145 WD
Earth Bull: 4 wins
Pegasus: 6 wins
0 instances of pegasus being KO'd
Only 10 rounds each, so it's not conclusive. For example, there were instances of MB being knocked into the wall, whereas it would have been a KO if there had been a pocket. I would guess that if more tests were done the results would be even closer. Anyway, I saw no significant balance issues with MB. MB and WD behaved very similarly.