This is what i did. Dumped rafactors in cydea boss fight. idied spiderlings and search them in the code of giles.cs. There i changed priority of cydea to 10000 and priority of spiderlings to -3000, yet the bot keeps attacking spiderlings when they are in range. There is some issue that is causing him to "always" prioritize white trash that is near him...
update: well blacklisting spiderlings seems to worked, shouldn't this also be true for fallen grunts? But when i think of it, all that blacklisting does is prevent the char from main-attacking the object (spiderling in this case) but he will use rend/revenge when available. Oh well, i just skip skycrown and stonefot, too much trash and too little elites anyway.