Something I keep seeing happen in general is that a lot of people misunderstand how Clemency works. What I thought at first, and a lot of people still do, is that you basically have two separate Hand spells of each type. Therefore if you alternated them you could HoP every 2.5 min. This is wrong in the long term.
What's misleading is that when you have consumed one use, wait a bit, and then use the spell again. The first use will have been partially charged up from that delay and make it look like it will be ready faster.
Example with HoP:
Cast charge '1'.
Wait 150s (2.5min).
Since you've waited you'll be able to recast '1' in another 150s so we'll do that
Now leading up to this you were on 1/2 of one charge so when you cast '1' again you're totally tapped out.
So for the first few uses at the start it looks like you can use it every 150s but that's cause the partial recharge carries over and tricks you.
Another way of looking at it is imagining that you have a hidden bar with 600 (in the case of HoP) 'units'. You gain 1 unit a second and it costs 300 units to cast 1 HoP. Eventually you're going to get to the point of just having to wait 300s to cast HoP again. And at that point it will be a minimum of 300s each time. Unless of course you never cast it more frequently then 300s.
Applying this concept to my previous example:
Cast charge '1'. (300 units)
Wait 150s (450 units)
Cast '2'. (150 units)
Wait 150s (300 units)
Cast '1'. (0 units)
The best example is that the two charges work like a pair of DK runes (of the same type).
You easily test this out with different times of course by grabbing Clemency and playing with Hand of Freedom.
This also explains why afer a wipe where you've used it twice, only one charge gets 'refreshed'. If they were independent then both uses would come off CD afterwards.
Once I realized how the talent actually functioned I lost interest in it greatly as protection. Especially with regards to self clearing effects with Divine Shield, and the Divine Purpose bonus, I think Unbreakable Spirit is a far better option.