Vampiric Grenth

Cracked Armor + Grenth Aura seems anti-synergistic as one makes your armor sensitive damage improve, while the other converts your armor sensitive damage into life steal.

Balth Rage is pretty neat-o for charging Heart of Fury immediately assuming your hitting the target with an energy tear down skill and striking two foes (or striking 1 foe two times). as the poster above me described, I would think it would be more useful then HotHF. I'll try running it and see. My thinking though was that HoHF's Burning lasts longer, and has the Holy damage packet on cast, and since both have the same recharge, that over time you'd do more damage with HoHF, especially given that adrenaline gain with a scythe is not terribly difficult lol.

I was also thinking of subbing in Banishing Strike for the third attack skill, and put Pious Haste in for Heart of Fury. This would give an energy based attack and IAS that would help in areas with Adrenaline denial, such as EVERY HM Iboga area lol.

I guess it depends on preference. But it could work well, flash Balth or HoHF, use PH, then go to work! PH when tearing a chant at 11 Mysticism would last exactly 10 seconds, which would sync up well with the recharge on either HoHF or Balth.

Cracked Armor + Grenth Aura seems anti-synergistic as one makes your armor sensitive damage improve, while the other converts your armor sensitive damage into life steal.

Balth Rage is pretty neat-o for charging Heart of Fury immediately assuming your hitting the target with an energy tear down skill and striking two foes (or striking 1 foe two times). as the poster above me described, I would think it would be more useful then HotHF.
I use a similar build, although a more tankish variant, cracked armor isn't necessarily a bad thing. While it may not provide much benefit to the dervish using this build in HM your party will be happier, particularly the ele's.

As far as I can tell, Grenth's Aura doesn't actually interact with your damage at all. It just looks at the total damage result after armor calculations, subtracts its fixed amount and adds the same as life steal. It neither helps you "ignore" armor, nor un-synergizes with cracked armor in any way. It might have interacted badly with the old damage multipliers, but those were all hit with the derv update. As far as PvE is concerned though, all the skill seems to do is self healing, which is pretty bad in a full team compared to even a few seconds of cracked armor, burning, adrenaline, or whatever. With that said, Cracked Armor doesn't hinder / become irrelevant for the build. I retract my statement.

I just want to mention that when using the Grenth skills' life steals as the primary source of damage (compounded with the -dmg), Scythe mastery isn't really all that necessary, imho.
I think something like twin moon sweep and auro of holy might could be swapped out for something else, perhaps to make use of a secondary profession a bit more. Nope, Scythe Mastery is still quite necessary. Without scythe mastery your gimping your scythe skills (Wearying Strike / Irresistible Sweep, Reap Impurities as examples). In PvP, you usually don't have buffs like Str+Honor, orders, etc etc, but in PvE you will (or at least should), and it will negate the damage reduction from G-Aura, this makes your scythe swings hit for near full damage assuming you placed points into the attribute.

The marginal gain from +1 or +2 in Mysticism and Wind Prayers that you gain by dropping the scythe attribute, or the inferior utility skills (in an age of 7 heroes) that you could spec into with a secondary swap come up short in comparison to speccing into Scythe Mastery.

Assuming I am removing a flash enchantment every ~5 seconds, I would never swap out AoHM unless there is heavy enchant denial, No secondary skill can match the aoe non-scatter packet damage produced by this effect passively (Unless your refreshing AoHM, you don't have to stop attacking).

Since Twin Moon activates Aura of Grenth + Avatar of Grenth twice, and does this irrespective of your scythe mastery level I see little reason why you would remove it.

In terms of secondary use.....what secondary use? Anything a Warrior secondary offers a Derv primary has access to, Ranger/Assassin utility is useless, Monk/Rit is unneeded. Ele+Mesmer+Necro Cast time skills = no attacking during those periods (greatly devaluing the use of your primary), Paragon skills in general are underwhelming (and costly on non paras). Your better off sticking to your primary, the age of secondary use, at least for dervishes is pretty much over in PvE.