Keep in mind, that unless it was fixed,stealth skill is currently set to be a bit high. So much so, that stacking too many increases that affect it will cause the value to rollover.

If i'm dealing with more than 1 target i always fire at the furthest one, and the other target always runs to that spot, not to me. Even when I see a target in a room and it walks out of sight, if i shoot an arrow into the room the taget runs to the arrow, not me. i'm only about 80 in sneak but with boots for an enhancement.

I don't get insta detected.
But I do get found like 5-10 seconds after firing my shot from a sneaking position, no matter where I hide, or move, even with a sneak level of 80

I'm on PC and I haven't had any issues like this. If anything, I'm even harder to find now. I was snuck down, and literally had just shot a Bandit, and his two companions ran RIGHT PAST ME, I freaking pick-pocketed both of them, then shot em both in the back. Just got done "The White Phial" quest, and the Draugr couldn't find me for squat, even 2 feet in front of me, and yes I exclusively use a bow(My melee skills aren't even above 20).

Yea cuz those are the ONLY two alternatives. No they absolutely shouldn't insta spot me, it renders playing as a stealth character absolutely useless if you can't actually defeat more than one enemy before having to engage in direct combat.
And it seems this only happens to a few people then, which is even stranger :S I wish I could find a solution to this..

i m on a pc but didn't notice anything so drastic , however if you target a group of humans , they tend to be more alert , even more than before the patch, especially if you can't instant kill your target , i always try to move back into hiding when doing this maybe that way i never noticed

Hm I'll try to be really careful and going into hiding instnatly I guess, I'll get back to you with an update to see if it works somehow

Makes sense in real life. First off the twang of the bow and the arrow thudding into the target would make noise, then the target would scream or groan in pain before dying (remember, nobody there to clamp his/her/it's mouth shut. The only way to be stealthy would be to always hit areas that are instantly lethal (temple for example), or ares that keep the target from making noise (i.e. throat).

which is why they should go into seatrch mode (which they used to do I might add) but instantly knowing where I am not only makes using a bow in stealth somewhat useless compared to a dagger, it also makes no sense