Well, the additional damage potential of Piling On is Obvious, but the matter comes more from the fact that it's the only proper damage potential in the team right now (with the Troll taking a frikkin' ten games to get to that first skill), so the Blitzer will be a target in general. Survivability (especially with two dead and one retired Skaven in two games, with minimal income to hire some new bodies) is therefor an important factor for me.
Dr. Von Richten, who had his Undead experience first-hand that not having Piling On can also do a lot of damage (

), knows who will be coaching the Chaos I am facing next, and I don't fancy losing the Blitzer due to a piling on at the wrong moment.
As for not going with Piling On at all; I play Underworld in a FUMBBL league as well and my best Blitzer to date ran with Blodge, Tackle, Horns, Claw and Mighty Blow... Two seasons of absolute destruction that didn't require Piling On at all.
Still, this all gives me enough to think about.
