Ret is certainly losing mobility, Seasoned Warhorse is 1 second compare to the 3 seconds from the conduit. Now you could say having access to Cavalier makes up for it, but it doesn’t. Cavalier is a fraud of a talent, it doesn’t give you two uses of Divine Steed on separate 45 seconds Cooldowns. It just allows you store one extra use if you haven’t used Divine Steed in the last 1 minute and 30 seconds. Which is unbelievably lousy, making it utterly pointless. If the talent Clemency back in MoP(which gave you double uses of Hand of Freedom, Blessing of Protection ect.)was like this no one would have taken it, as it would have been pure garbage.
Also Ret is losing Echoing Blessing, which added to mobility by giving Hand of Freedom a speed increase during and for 8 seconds afterwards. Which for some unfathomable reason is now exclusively a holy talent and not in the class tree. As if Ret and Prot never used the conduit. Which by the way the class tree is designed, holy paladins can skip every single ability Echoing Blessing affects(yep you can actually choose not to talent Hand of Freedom, Blessing of Sacrifice and Blessing of Protection in the class tree. But still talent Echoing Blessing in the holy tree. You can also do the same with Hammer of Wrath and Veneration)