[GAMEPLAY] Tahm Passive bug

So I recently played a game with Tahm as support in the bot lane with Kalista . I noticed that if you are Oathsworn with her that her W passive overwrites or takes priority over Tahm's passive. This may be intended but it makes it so he cant use his passive at all when he is by himself, the only time his passive would work is if Kalista's W passive was on cd. This made it near impossible for me to harass the enemy team without Kalista and when i did I couldnt use the upgraded ability's that my passive would provide. I couldn't even control scuttle crab like Phreak said i should :( Please help, I think Tahm and Kalista could be a great combo.