If necros were as OP and "broken" as everyone keeps pretending they are because they can't steamroll them in a single rotation, everyone would be playing them to stay competitive. Just stop already. When people who actually counterplay see you complaining like that, it looks bad. Balance is focused on high-end play because you don't balance around people not playing correctly. That would be ridiculous.
Are their rotations and gameplay simple? Yes. Are they broken? Not a chance. Grab some cleanse and start learning to corrupt boons. You'll be fine.