So, a friend and I were messing around in customs vs. each other for three games in a row. Each time, he played an AP champion (Akali/Morde) while I played AD champs (Riven/Zed/Yasuo). In duels, they generally didn't go in my favor with mistakes and such. Yet as soon as I built Maw, the playing field was very even. Even at level 18, the dueling capabilities between us were kept even solely by the fact that Maw's shield/passive kicked in and helped me win. It wasn't 100% of the time, but at least 65-70% were solely because of Maw's shield and bonus stats.
That alone doesn't confirm my point, so we tested whether I could take Baron as Yasuo solo. I had IE, BT, Death's Dance, Maw, TriForce, and Berserker's. I was on the verge of dying, as the lifesteal wasn't enough to mitigate the damage I was taking, until Maw kicked in. All of a sudden, I could lifesteal more than Baron could damage me and secure the baron solo. I know that in past iterations of Yasuo specifically, he isn't capable of soloing Baron without something being imbalanced (in past patches, it was original Warlord's). The fact this is possible, with a build that only had 2 lifesteal items, with a third item giving bonus stats that allowed me to overcome the damage taken, and the third item had everything to do with the turn of events, makes both of us feel Maw is in a powerful state. The 3250 price point, for the raw stats it gives plus the invaluable passive/shield it provides the item holder, make it one of the currently best dueling items to buy in the game. Since it's intended for more of a bruiser fighter, and yet even assassin-like champions such as Riven/Yasuo can utilize it and completely win duels, I feel it's overtuned and needs some stat mitigation/passive tuning in order to bring it back in line. Otherwise, League of Maw will be very prominent.