i tried to run 3 - if you only cap them all once a week it is doable, but you will always be “behind”. I tried to start doing N’zoth and found myself staying up until 2-3 am (i play in the evenings). Even casually i was putting in some hours (corona…you jacked up my sleep schedule).
could not do 3. Luckily i get more enjoyment from playing alts in this game so I just randomly swap around. If you are ok with mediocre character development play 3. (2 would be the most I would recommend if you have a life)
minimum time per character per week: 1-2 hour quests, assaults. 1-2 hour visions, 2-3 hours pvp, 3-4 hours heroic raid, 1 hour for single +15 dungeon = 8-12 hours - and I may be forgetting stuff (echo grind, spamming mythic dungeon for gear or specific gear, etc). That is per character for basic progression. If you are doing islands, darkshore, etc…even more time.
3 toons = 24-36 hours per week