In my experience a follower can, and will be, detected when the stealthy player is not. I have on many occasions had bad guys rushing straight past me to get at my follower. In fact, I am now starting to use this as a tactic: I go sneaky in front, Mjoll clumps along behind, bad guys spot her and as they rush past me I stab with the every-trusty daggers for a one-hit kill without having to do any hard work for it - works a treat with Falmer, not sure it would with the Forsworn though .
In my experience a follower can, and will be, detected when the stealthy player is not. I have on many occasions had bad guys rushing straight past me to get at my follower. In fact, I am now starting to use this as a tactic: I go sneaky in front, Mjoll clumps along behind, bad guys spot her and as they rush past me I stab with the every-trusty daggers for a one-hit kill without having to do any hard work for it - works a treat with Falmer, not sure it would with the Forsworn though .