Aura uses it's eyes to know when to reproduce, it surounds itself with 3 smaller bots, but if it looses sight of them it creates new ones...
So when the eye range is reduced considerably it will quickly loose sight of the offspring even though they should be within range.
Guardian also fails against anything that fires at it from a longer range, since it can't see too far, but counter leeching will also work on it now (I think the first cycle was safe in older versions maybe, making it possible to drain nrg for one cycle and then break the tie.)
Etch broke down because shots where weakened for small bots.
Excalibur broke down lately... not sure if it's related to in/out values used for the reactive armor, or if it's one of it's vars that got put to use. (Should be easy to figure out, excalibur is a rather short bot)
And reaper has also dropped in performance also a small bot using shots...
So I think the old top 5 are all broken by now... so I'd guess a lot of the other bots are having problems aswell...
Also you can fix Aura if you want, just disable the broken repro gene (It has 2 repro genes, one of them no longer works with the new eyes) and ofcourse replace the gene with a propper working repro gene. Excalibur could probably be fixed too... don't see much hope for the other 3 though, too much work and major changes would have to be made.