I love absolutely everything about this but I have had one thing that is slightly bothersome since I saw it first.
I personally prefer having the extended tooltips on. It makes it super easy to see exactly what's going on. I have one minor quip about it because of this. It's hard to see exactly what the final number will be when it's just ratios. Could you include after all the ratios and such the total number of damage, healing, etc that will be done at the end? For example:
50 (+1.5 AP) (+.01 AD) [96] Physical Damage
That way it's easy to see both the source of the number AND what it will actually do in the end.
One other very minor thing that I haven't really decided if I would prefer or not: percents. Would it possibly be less confusing to see the percentage of AP rather than a decimal? For ex from before:
50 (+150% AP) (+10% AD) [96] Physical Damage
Not totally sure which I prefer, but I think the second one makes it more clear...