I've always read that the hamstrings should be about 70% as strong as the quads to prevent imbalances that would affect the knee in particular. More recently, I've seen 50-80% cited as the 'normal'range (but it's probably not as good to be at the bottom of the normal range, so I think 65-70% is still a good ratio to go for).
Most of the time, the problem is that the quads are much stronger than the hamstrings, because the former are worked more or used more in a sport, and the latter are ignored or underworked.
DOMS is not a good guide to judge weather the muscles are in balance. The best way would be to use a leg curl/extension machine, find out what your X-rep (X is any number, say '10') maximum is for each exercise, then divide the ham curl number by the quad extension number to see what percentage you get. (for example, just to make it easy!, let's say you can do 10 leg extensions at 50# and 10 ham curls at 30#, that would end up being a 60% ratio, which is good...but it wouldn't hurt to strengthen the hams a bit more. If instead, you can only curl 20# for 10 reps, that gives a 40% ratio, which is too low, and can lead to injuries.)
You could approximate the same test an home, strapping on an ankle weight and doing as many extensions and curls as you can. If you take weight used x number of reps for each exercise, then divide the total for the hamstrings by the total for the quads, I think you'd get an approximate ratio for ham-to-quad strength (though it probably will not be as accurate as the machine version, where you can manipulate the actual weights more).
HTH
