I was aware of the cloak’s stats not being 1:1 with our main and our alts, but I thought that the cloak would retroactively upgrade my already created alts. I noticed that the exp % buff stayed the same (around 16%) as my main got the cloak achievements.
I made a new character and they had a cloak at 50% exp.
Does that mean I have to delete all of my alts and recreate them to gain better cloak stats 
To be blunt, unfortunately yes from my understanding. My 2nd Time runner I didn’t know that, and I created the character when my main time runner was around XI because I wanted to get some rested experience built up. My 1st cloak is now XII with a max experience buff of 113%. My 2nd time running character cloak is experience buff of 159%.
I had thought that the stats would carry between characters the same but it’s not true only certain stats like main statistic, stamina and base experience gain. My 3rd character cloak had +250 strength and +750 stamina and 100% base experience gain. Well not sure if the stamina and strength are not flip flopped because my third character gear is all missing after I logged out last night and in this morning.
it retroactively upgraded on the PTR but it usually took a few minutes to do so, like you can complete a quest and then it will upgrade.
I am not sure it does on live since I made an alt when my character was around 55 with about a 50% xp increase. My alt easily caught up to my first characters experience though and it is only 28 - they both have close to 100.
They intentionally changed it from the PTR to not be 1:1 and only be tied to achievements. Blizzard intentionally stopped it from sharing between characters like they told us it would, so they pulled a bait and switch. Many people have stopped playing the mode because of it since they haven’t said a word about it, but nerfed the frog farm after a handful of people got to become OP while everyone else is still way behind.
Try taking the cloak off on your alts and requipping after you get the 4200 thread achieve.
I made alts all on the same day as my main and thought I would have to recreate them to get a new cloak. but taking it off and putting it on took the buffs from like 13% xp to the 100% xp.
The cloak should have been completely account wide. Especially after this disaster with the frog farming. Why the hell shouldnt someone be able to just pool the power of alts into a mildly powerful cloak compared to people with several million health.
Man, i changed to an alt to see the exp buff after I got that 2200 achieve and it’s only at 59%, went up from 16%. This guy is my highest and the buff is at 75%.
I dont understand anything and this sucks.
Thank you very much this fixed it!
I took off the cloak and when I put it back on, the stats were caught up to my achievement progress.
Thank you 
Just remove the cloak (put it into your bags) and then re-equip it. The stats and exp % will refresh. You don’t have to restart your whole character.
You are AWESOME!! I’m an altoholic so i had 4 toons before the first one hit 30.