That's the point!
Hence, the following suggestion:
Provided that we all wanna keep chat and TS (to abandon this would btw solve the revenge fleet issue immediately - however, a very drastic way, I admit ;-), maybe a zone/circle could be implemented around any battle location in OW, in which only "in battle speed" would be possible. Maybe with the diameter of the equivalent of the arena. So that any revenge fleet could approach as well only with battle speed when entering this "pre-arena" zone (adjust battle entry timer correspondingly). Thus, if a skilled ganker is fast enough to capture/sink his victim in short time, he - being dropped as well in this zone after battle - might have a realistic chance to escape from the approaching revengers, while the revenge fleet might have a realistic chance to get him...
The OW warp speed is only necessary because of the big map. But here imho a solution must be found for the transition phase from macro world into micro world...