The item for Elder scrolls online currently does not route traffic through mudfish.
I think you may need to update it.
My ping in ESO is affected in full VPN mode (e.g. using a RU server gives me >500 ping to NA server from AU), but not at all when using the equipped item (fastconnect or normal). Node selection makes no difference.
Equipping the ESO item just has no effect on ESO traffic.
I have no issues with mudfish in any other games (e.g. ffxiv).