Galio's W should work like Nunu's W and Morde's W
If you cast it on ally it also casts it on yourself, giving the Ally 50% of the Heal and 50% of the Armor and MR bonuses while also giving Galio only 50% of the heal amount per hit from an Ally
This would give 15/22.5/30/37.5/45 Armor and MR to an Ally This would heal an ally for a max of 62.5/100/137.5/175/212.5 (+ 75% AP)
POSSIBLY adjusting the healing to take more hits to get a full heal to balance it
Adjust healing to 12.5/20/27.5/35/42.5 (+ 15% AP) per hit but 10% weaker per consecutive rather than 20% weaker so that the cap is the same but the healing per hit is much less than on live. This doesn't really effect Lane Galio because he mostly hits cap fast from Minion aggro.
This would allow Support Galio to be playable without making him ridiculous.
With this change you could also make his W give 50/60/70/80/90 instead of 30/45/60/75/90
