I have had this problem with a chinese E3D clone also with a Bowden extruder. Due to the bowden tube I needed around 6 mm retraction to counter the oozing. However, which such high retractions, hot rubbery filament is pulled up too high and then cools and sets higher up in the heat throat causing a jam (it sticks to the metal wall). My solution was to convert the all metal heat-throat for a ptfe lined one, which solved my problem completely.

My personal conclusion is that for an all-metal hotend you either need to be lucky with respect to the heat-throat (seems to be a hit and miss issue), or you need a direct drive (no bowden) extruder so that you can keep the retractions to less than 2mm.