There appears to be something wrong with how Sylas' ult works with AD ults. Either the tooltop is wrong, or I have a fundamental misunderstanding of how Sylas's ult scales.
So the ult says that an AD scaling will grant a .5 AP ratio for every 1 bonus AD ratio. My interpretation of that would be that for every bonus AD scaling his ult will scale half as well with AP as it normally does with AD. My first throught was to test it using Caitlyn's ult, which has a 200% bonus AD ratio, which I would presume would mean a 100% AP scaling. But instead it had an 80% AP scaling, which would suggest .4 AP for every 1 bonus AD.
Furthermore, I tried it with Wukong whose ult has a 110% total AD scaling, and got a 33% AP scaling in return, which would mean .3 for every 1 total AD.
Therefore, one aspect of the tooltips has to be wrong. EIther the AD to AP conversion ratio is incorrect, or the tooltips telling you how much damage your abilities will do (which is where I got the values I used).
As I side note, I really don't understand why total AD scales worse than bonus AD, when champions will always have a higher total AD stat than bonus AD, which I would think would mean total AD would instead translate to a higher AP ratio.
Note: I would have posted in the Sylas bug thread, but for some reason I cannot post comments. It simply doesn't do anything when I click post.