Can go without giving my feedback on the new galio,... I know I gonna miss the old skin andI don't really like the muscle dude high stature with goofy smile new skin,... at last that's smile isnt really something you notice ingame.
(TL;DR at the end)
I'll start with what I like... his Q is way more gargoylesque if I can say so.
his E his make more sense then the stange speed buff trail tornado, that I always thought should be made into Janna's, still I think that you might add to it that it leave the same speed buff trail behind him as he rush forward, that would be nice and keep a little flavor of the last utilities of galio.
His Ult becoming his W taunt is something that I was waiting for since an age.
And finally his ult is nice, but I would like it to be castable on allied structures aswell as champions, so to go more with the Gargoyle/gardian theme, and maybe recall it Guardian's entrance rather then Hero...
Now you see where I'm kinda disappointed;
You removed the MR-AP sinergy.
If you wanna still go for a AP mid tank with galio,
I would have made his innate to be:
shield of durand... gain 15% AP as MR
so that would make him able to build AP mid and still be Tanky vs mages; then scale all his abilities damages on AP ratio base on that and even make that his abilities damages Scales on MR aswell; so building MR tank would still give him a little damage increase.
the magic shield from the passive of W is just something that I will not considere, 12 seconds without receiving damages...!! that's just a little extra health vs mages, that look like a Malphite's MR version copy, why have you gone this way?
making the W called Colossal Smash and the innate becoming the passive of it, and the charge up W release to just release a smash on the ground with the taunt effect, would make more sense.
Going this way would allow and enforce galio much more to go AP and be still a mid anti mage tank, and make him a Base guardian.
Personnally I would make him more a structure oriented rather then a champion one because I already forsee that it gonna be used as a ganking/counter-gank tool for galio to rescue allies bot top or jungle.
To make it on structure would force people to put wards (including wards into the structures targettable); but I'm pretty sure that this view would not be shared by many.
TL;DR...
Switch innate with W passive,
Make the innate "Shield of Durand" that galio gain 15% AP as MR;
scale all damage on MR and reduce the AP scaling of them.
Make W release "Colossal Smash" release to smash the ground instead of target and taunt.
Make the Ult castable on allied structures.