Root rot method is best when you have the AA root which has a lower check vs mob magic resistance. Most of our root spells have a higher check and they get resisted maddeningly often and wear off too quickly unless they've changed that. If you don't have AA root then reverse aggro kiting with rogue pet backstabbing was the way but haven't done it in a long time...I think they changed it so mobs will turn and aggro pet almost immediately now?
If you want to see what a solo necro can do with just a merc healer look up Xellene on youtube. There isn't much he cannot do. He plays on the test server and loves to chat about the game and necros. He has great advice for all things necro. They are very very powerful
If he is just starting out, he was probably informed to get a tank merc, which is solid advice. At low levels, you want a tank merc. Up until around level 65, a J1 (journeyman tier 1) tank mercenary has INCREDIBLY high tanking ability and super fast hp regen. It will basically powerlevel any character up to about level 65. Somewhere around level 65-67 though, they lose the super fast regen, and rapidly lose their uber tanking ability. That is when you would want to change to a healer merc. The problem with mercenaries post level 65, though, is their performance is not very good, and they do take part of your xp. To maximize xp, most necros just use their healer mercs to buff them/their pet, then put it away while grinding xp.
I strongly recommend fear kiting until you can't land fear on mobs anymore. No merc to steal XP and if it goes south, you can still feign death to save your own hide (Sorry Jebober!)
