I'm only on about 2k kills and I have had 2 silvers drop from summons.I think the game was making it up for me for only dropping 1 healer a couple of events back with a Christopher (I didn't have one!) and Dorca.

Best I've done is 497 kills. A couple of red flyers leaked through. Since then I fixed the leak problem (a subtle change in deployment) and now I can't beat the liches like I did the first time LOL