Sum 2267 is right smack dab in the middle of the range (by arena experiment) that gives delay 10 even. So I've got one sum 2267 goblin who's either doing delay 10 even or very, very close, and another one who's doing ~10.5. Neither goblin shows any wounds or scars.
I don't think I'm going to bother working on the formula further-- it should give accurate results plus or minus one, and if there are rounding artifacts, its hard to say where exactly in the algorithm the rounding is happening. It would take testing a lot of different hypotheses and comparing a lot of data for very little payoff.
Probably in a couple of days I'll finally get around to making a wiki account (have just been signing with IP) and post the formula in some relevant talk page-- need an account to make a talk page. Certainly, if you do any work on making a better formula, write it up!
I got some likely sums for integer delays, and I plan on using that to try and figure out some goblin-based clock generators, see if I can do anything useful with it. There are a few other problems to sort out with this-- like why they fall down when a long path is suddenly blocked off but not when a short path is suddenly blocked off. I'll be able to see if there are other goblins that don't match anticipated delay during these tests, and maybe I'll find the common feature. In the meantime, the 10.5 delay goblin seems like an anomaly. I'll post more if I figure something out.
(In case you're curious, likely integer delay sums are 421, 790, 1160, 1529, 1898.5(could go either way), 2267, 2637, 3006.5, 3376, 3745. Could confirm some of those in arena, most provide non-integer adventure speeds.)
Thanks for your help, dree! I don't know about you, but I benefit a lot from people doing parallel experiments-- important to compare data, verify and see what doesn't work, and other people help set me straight when I make a stupid mistake.