Sion bug, Ravenous/Tiamat + Glory In Death

The bug occurs when Sion dies, after Glory in Death activates, his auto attacks no longer proc the Cleave passive for the first 3-4 seconds after death.

I tested this out in a custom, I farmed up until I had a Tiamat, wandered into the jungle and executed myself on the raptors. Started auto attacking and sure enough, no aoe. Killed the whole squad by activating the crescent then finishing them off with autos. Tried a second time with the raptors in the enemy jungle, result was the same, no aoe melee.

I noticed however on the last punch it caused the usual aoe splash. So I went to red buff, executed, then proceeded to attack one time, back up, rinse and repeat to keep the creeps alive, and lo and behold, if you manage to stay alive for several seconds, the cleave passive will reactivate after a while. For thoroughness I retried this a handful of times and got the exact same result. If you survive long enough your Tiamat/Ravenous will reactivate, but it is useless the first several seconds of your passive.

edit

I did some more testing, other on hit effects seem to be working, Tried frozen mallet and wits end. However Ravenous Hydra seems completely random as to when its passive wants to start working after death, I have seen it start on the first blow after dying, and I've wailed away at dragon and blue buff for my entire life bar with no splash effect. Sometimes its right after the first hit, sometimes several seconds, sometimes not for as long as I can stay alive.

I have long thought Ravenous Hydra would go well with his passive on a tank build(He is my Top Main), but every time I tried it on rift it felt underwhelming so I avoided it. Just this evening I was on an ARAM and grabbed it and noticed my attacks did not finish off the two "extremely" low life targets beside my main target and began to wonder if it felt underwhelming because it wasn't working. Now I know it was not, could you guys test and see if on hit effects are not working on him in Glory In Death for the first portion for some reason? And hopefully fix him? Thanks much.