I'm at level 44, Alliance Members 28 Attack 101K, Defence 100K. Not a farmer though just do Epic Boss event only once I get over level 100 when it's extremely hard I'll begin LTQ's as I've put all Skill Points towards Hero Strength.
When you attack someone it shows you "Strongest Units and Items: 216" just times that by 100 = 21,600 I Believe that should be your absolute minimum. But I like to keep my stats three times the minimum all the time so I only add on alliance members as I gain more units from boss events. That's my strategy anyways!