Dual-box(is this ok?)

[Amiaze]

Generally speaking, it's not accepted anywhere. I've never had someone admit to doing this, but I've been in at least two dungeon runs that went painfully slow. When I started watching the DPS, I noticed that one would move and attack while the other stood perfectly still. In both instances, one character would do a set rotation before ceasing to attack completely for several seconds.

I'm not sure that this is against the ToS since, as you said, they're legitimate characters. Still, I wouldn't risk it, especially if they're not on the same account. People often use this method to powerlevel and then sell characters later.

[Niwashi]

Generally speaking, it's not accepted anywhere. I've never had someone admit to doing this, but I've been in at least two dungeon runs that went painfully slow. When I started watching the DPS, I noticed that one would move and attack while the other stood perfectly still. In both instances, one character would do a set rotation before ceasing to attack completely for several seconds.

I'm not sure that this is against the ToS since, as you said, they're legitimate characters. Still, I wouldn't risk it, especially if they're not on the same account. People often use this method to powerlevel and then sell characters later.

That's a different type of dual-boxing than the OP is talking about. If you have two different controllers (or two mouses/keyboards, whichever you're using) and alternating between controlling one character and then the other, that's both definitely allowed by the rules and definitely not allowed by most player parties, since, as you pointed out, it turns into each character standing idle half the time. It's perfectly permissible for solo play, though.

The OP has a single controller controlling multiple characters at the same time, and I'm not quite as confident that SE's rules would allow that or whether it would count as automating one of the two characters. (I think it would technically be allowed, but I'm not with SE so can't confirm their stance on it.)

Oh, and in either case, they have to be on different accounts. You can't be logged in more than once with the same account.