Is a temperature of 100-105C ok for 4670 under load?

It is perfect you can now boil water on it.

To hot, you shouldnt allow your GPU to hit 100C. GPU's are generally made to run hotter, but thats to much.

Two quick things to check, make sure your GPU fan is on HIGH while stress testing or doing anything graphic intense.

Other thing, your case ventilation; intake and outtake. Most likly you arn't water cooling them, so make sure you have air blowing on to the cards from the front and being pushed out the back. You have to keep the air in the case moving, otherwise the GPU's will just heat the crap out of your case.

I try to hide all my cables, and try to have no cables blocking fans.

I have 2x 120mm fans blowing directly on my 2x GTX 295's. One under them and one directly in front of them.

I single cable shouldn't hinder to much, however just use your hand to check.

My 2 gtx 295 hit about 68-75c on full load depending on how long i keep them there, and between 73-79c while using with a 20% overclock on them.

What case are you using. I have 3x 120mm intake fans, 2x 120mm exhaust fans, 1x 200mm exhaust fan, and 4x 120mm internal fans (2 on cpu and 2 on gpu)

That funnel thing is generally to help along the stock CPU cooler. Sounds like you could put a few more fans in your case though. First, blow out any dust in your case. Also make sure that the back of your case isn't up against a wall as that will reduce the cases ability to exhaust hot air out the back.

Another thing i noticed is that while idle the temp is 53-55C with fan speed 12%. On viewing video at full screen for 10 minutes it went upto 85C. And on graphics intensive gaming the it shot beyon 105 and The PC shutdown.

I would never let your GPU fan speed drop to 12%, I manually control mine at all times. I adjust it to what im doing, desktop = 40%, video= 60%, gaming= 70-80%, Benchmarking= 80% +.

But you need to tell us about your case, so we can rule it out as the culprit or not.