The Dovahkiin can slow down time to where enemies move much slower. That's close to stopping time.
Ok slowing down and stopping are NOT close to the same thing. Tell you what, go run a red light, but slow down as you do so. When the Police Officer pulls you off and gets onto you for running the red light, say "yeah but I slowed down, that's practically the same thing." Tell me how that works out for you.
Secondly, he only does so to a very minor extent. The Dovahkiin himself is slowed by the effect aswell. Turbo or Implant GRX slow time down to an equal extent BUT the Courier isn't slowed down at all. Whereas Dovahkiin slows time to 10% but he himself is only moving at ~40% speed, the Courier slows his perception of time to 35%, but isn't slowed down himself AT ALL. The Courier himself also runs incredibly fast on his own (10% faster than someone with no armor/light armor; I would hope we can all agree the COURIER has the Travel Light perk.
). Whereas Dovahkiin can only slow time for 16 seconds once per 60 seconds, Implant GRX alone (without Turbo doses) provides a full 2 minutes, 20 seconds of a slowed perception of time. VATS is another issue entirely, as it seems to guarentee you hit first.
More importantly, to detect an enemy's life force, the Dovahkiin either needs to CONSTANTLY keep a spell up (occupying one hand; no bows allowed if he uses this method) or use a shout, thus occupying his shout slot, since the Courier can just remain stealthed with a Stealth boy.
In the end you've got the Courier at maximum range firing CONSTANT (Rushing Water and Turbo) 600 damage rounds that have a decent chance of knockdown at the Dovahkiin (190 base with explosive rounds, 300 on a crit (guarenteed by sneak), 600 for a headshot, reduced to 20% by the Dovahkiin's armor for 120 damage per shot, 76 for non-crits) able to STILL kite back and dodge at decent speeds and KEEP that speed for longer, keeping the gap between them constant.
We're -literally- talking about a scenario where the Courier could potentially kill the Dovahkiin before he even FINISHES the shout. The Courier has basically slowed the Dovahkiin's shout speed to 35% of it's original, while also multiplying his own firing speed several fold. I believe the Courier's attack speed would see a 250% increase, which is beyond ridiculous. In 2-3 seconds time the Dovahkiin would be hit with a full clip from an AMR, for a total of up to 960 damage in the time it takes the Dovahkiin just to realize he's being hit and complete his shout,
IF the explosion doesn't knock him on his ass first. Even if he survives, he's still got only 16 seconds to locate the Courier, run up to him and hit him; hell, would the life detect spell the Dragonborn has even detect a target that far out? This is literally maxed range...
The Courier WILL get the first strike because while the Dovahkiin cannot keep all his abilities up at once (stealth detection, invisibility, slowed time), the Courier can. The Courier can spam stealth boys and Turbo doses for days while his stealth detection is constant. If the Dovahkiin attempts to detect the Courier in stealth, then it's a big message that screams "I can't slow time because I just shouted, I'm incredibly vulnerable right now!" So basically the Dovahkiin is a sitting duck who has to react fast the moment he's hit, slow time, MOVE, and then detect, catch and kill the Courier within 16 seconds time, and it's a big "if" if his life detect spell would even reveal a target that far out from his location.
And this is with an AMR. We're not even talking about Esther yet....
He's screwed.