Grinding instances and selling all shards works okay for me. Plus I usually get decent cash for the aldor and scryter stuff that drops there too. I never go farming for mining nodes, herbs or primal whatevers i need. Always have an eye on the AH and buy cheap.
Remember that playing 5 accounts your goal must be to get money five times as fast as with one account. That will never work but gimping yourself by e.g. mining with one char have all other chars on follow needs no multiboxing.
Bucco