There's no room to max out 5/5 RoR. Two points must be put into Imp UP.
There's many advantages to playing in Unholy Presence, the most obvious being burst. However, there is many additional advantages. It's easy to read lists, I'll use a list. These are just the doggone obvious ones.
- The shorter GCD means it's also possible to outrun dispels, so you can completely lockdown a melee with Chains of Ice through dispels temporarily.
- +10% runes means you can generate runic power more quickly. You can also reapply diseases and chains more often.
- The shorter GCD allows you to use one rune moves, which generate much more runic power.
- You have more control over your timing of disease applications, since the shorter global allows you to rapidly reapply them. This makes it nearly impossible to dispel diseases.
- The Gargoyle and Pet attack 15% faster, and Corpse Explosion casts 15% faster.
- Shorter GCD allows more careful timing with abilities and allows you to kite without sacrificing damage output. Allows you to burst down mages, rogues, and any weak cloth/leather class more quickly.
- Empowered Rune Weapon is much more useful, because you're able to more rapidly use the new runes.
- Strangulate can be used to interrupt casts more reliably because of the shorter GCD.
- The additional movement speed allows you to kite/deadzone melee with impunity because you're faster than them, in addition to being able to overrun anyone without the same movement speed increase.
- Much more difficult to control a DK playing in Unholy Presence, because they can more rapidly utilize abilities before being CCd.
- Being able to cast chains faster means you can completely immobilize a mage, or any other caster or player.
- Much more survivability than in BP. In addition to being able to cast chains faster and more often, you can also more easily get diseases up to rotate Death Strikes. You can also cast Death Strike faster, meaning if you're eating chain stuns you can probably get three off before eating another one.
- The additional movement speed makes it much easier to land focus interrupts; furthermore, being able to proc desecration more rapidly gives your whole team breathing room.
- Can apply diseases more readily, vastly increasing the speed of a swap.
- Less reliant on diseases without maxed out points in RoR and WP and without the +15% dot damage from BP.
- Increased value of Chains of Ice through Chill of Winter. Can also generate 20 runic power for a fast AMS/IBF/Deathcoil on demand.
- Less cost for presence dancing; you have more runes to swap stances.
- The rune you need is up more often when the cooldown is one second less.
- You can more rapidly BS+BT for two Death Runes, allowing a quick 2x Chains of Ice or an extra Scourge Strike or Death Strike (or 2x PS).
- Reduces the 'stagger effect' of applying diseases and reaping. When you play in BP, you have to wait a global between Icy Touch and Plague Strike. This means you have to wait an extra 1.5 seconds to SS. This is just plain wasted damage. It's the same way with Blood Strike. This makes disease dispels in turn much less painful.
There's a little bit of overlap here, and there's many more advantages to playing in UP. Generally, in addition to being much burstier, the survivability is much better. Damage done while crowd controlled is much higher. Reliance on diseases is much lower.
I thought I should post this here, since so many players have been asking me what's up with my spec recently.
Normally I have an offspec that redirects one point from Impurity into Unholy Blight. It can't be dispelled so it ruins rogues. Also makes it just plain difficult for enemy healers to filter through all the dots and see when to dispel.
Sorry for the long list, I thought I should back up my point in as much detail as I could without making a textwall.