Did/doing some testing right now on the PTR:
1) Imp. Unholy Presence is not as good as it seems.
Test 1:
rune CD for single rune in BP: 10 seconds
rune CD w/ Imp UP: 9 seconds
Therefore the talent is working
Test 2:
IT spam on a lvl 65 test dummy (no chance of miss), looking at timing on first frost rune (burning the 2nd as well); 270ms latency
10 first frost runes in BP: 93 seconds
10 first frost runes w/ imp UP: 90 seconds
The 10 in BP should take 100 seconds. I repeated this a few times and got the same results. If you are hitting runes as they refresh (which you can do with 2h unholy because its not too crammed for GCDs) then the rune refresh is actually shorter than 10 seconds (remember that window that Blizzard built in for latency). The one second reduction in rune CD only appears to work on rune refreshes that are the full 10 second duration. Ideally this should be tested with an actual rotation, but you can't really do that because of the RNG of SS glyph. Regardless, the benefit from Imp. UP is going to be less than a 10% improvement in rune CD in most situations for this build. There is still the question of how much you value personal run speed though.