I would honestly just leave it as it is. I wager they are an effective support unit, especially in multiples, if there are sufficient enemy ships present. Aside from that, they are obviously good at pulling aggro, and sometimes you want that. The unit is boring because the attrition mechanic is boring. I don't think you can make it exciting or fun to use without making it horrendously overpowered.
I like the idea of an on-death effect though, since everything wants to attack it anyway. Explode with damage and range proportional to the total amount of attrition dealt? Might coax me into using it, at least. Though this might just turn them into Martyrs if you're not careful. Grav effect that Keith suggested might also work.
In any case, don't put engine damage on it. I'm not exactly looking forward to waiting for repairs on every single ship in my fleet to get their speed back.