T0astman, if you're not infuriated at heimerdingers pushing your lanes down, I guarantee you are not playing against good heimerdingers. As long as his grenade deals any damage to turrets at all, and as long as his own guns target enemy turrets, he will be the best pusher in the game.
He is pretty much banned 100% of the time in every ranked game, along with three of the following: Soraka, Shaco, Xin Zhao, and Shen.
Ashe's arrow does have an AOE slow... but that's not what matters. It's the fuck-all huge stun that matters. Also, she has FREE VISION WARDS YOU CAN SHOOT AT 2400 DISTANCE. FREE. NO MANA.
Her squishiness is now offset by her becoming better than teemo at scouting the map out, paired with her incredible item scaling (so long as you're a smart person and buy a BF Sword as your second item after doran's shield or whatever you got to start), makes her hands down the best ranged physical champion in the game right now.
EDIT: If you can't last hit, don't bother playing Ashe. She is one of the most important champions to get last hits with, every time you have the opportunity.