I need some help with placements of some abilities. If I run fire/fire it doesn't matter as much but if I want to run a front bar lightning staff and bb fire, would I put fetcher infection on the front bar or back bar? I get confused by the ancient knowledge passive. From my understanding, if I run fire staff on back bar and bar swap, the ancient knowledge passive will apply the lightning AoE buff to my abilities such as blockade and revenge from the back bar which are already placed? And then, would the front bar lightning staff buff Deep Fissure which will go off while on the front bar because its an AoE ability?

Why do people run fetcher infection on the back bar?

Im all confused lol, any help would be greatly appreciated!