I agree the most important thing is shot placement, however, to me there is a difference between mechanical and fixed blade broadheads. I used to shoot muzzy's, and loved them. I once shot a buck throught the front shoulder and knocked him right over, and I wouldn't take the same shot with a mechanical. I switched to Rocket Steel Heads, because I found they are easier to tune with the carbon shafts, and I've had good results with them.

Sounds to me like shot placement and shafts are more to blame here. I've shot many deer with aluminum and Carbon Express shafts, and I've never had one break. In fact, I've shot through mulitiple deer with the same Carbon Express shaft and its still in my quiver.