Patch 7.3 sep13 2017

Druid Order hall. + order hall advancement "travel form" = -20%
Carrot = -10%
saddle=-15%
=-45%

For longer duration (ex.:1 day 8hrs) the carrot is acurate.
But for shorter duration the carrot is not -10% instead it's approx -9.3% ex.: 14hrs=11hrs

Considering that an avg person sleeps 8hrs on 24 hrs of course you can do 2 missions in 1 day with an 11hrs mission but might be better to do a 14hs at 200% for twice the rewards than a 11hrs at 100%ish.

So it's pretty much useless (except for the travel form) at 1 follower 10+15 =25%
But might be real good at 3 followers -25% x3=-75% haven't tested it yet:) I don't know if this stacks with multiple followers. ex.: 3f at-25%+travel form 20%=-95% reduction time + each with 30% under 4hrs

This would mean a 14 hrs would be done in 0.7hr with a base 90% chance on any mission!

So I tested it and it has a diminishing return for exemple: (with a carot and a saddle on each follower) so 95% reduction but:

14h24 mission =1f (11:00) 2f(4:12) 3f(2:51)
total max minutes 864,
total calculated 95% reduction= 820min,
total in game deminished reduction 693min so ain't 95% but 80.2%

Nice they added items: under 8hr or 4hr it's +30% +40% so I added those 1 for each folowers and my mission sucess was 185% on most mission :)

Depends if you want to do more the same day or do a single pass each morning.

In my case I'm gonna stick with time reductions X3 followers:)