Buff Orb of Annihilation, please?

Doing some testing with this ability, this spell is not a very reliable one in the later half of the endgame quests. You have to stack it up to level 90 for it to even be considered reasonable. This is especially true for those who manage to get their hands ahold of an extremely rare relic version, which only gives a measly 5 to 10 (plus the +1 to all skills). There's a few ways this could be improved without changing it too much.

One of these alone should suffice.

Increase relic version from ranges (5-10) to (30-35). The rarity of this relic is plenty justification for this.
Increase damage gain per level to 150, reduce + to OoA amount given by necro wands (they easily get the largest boost)
Reduce mana cost to 2000

Just my two cents.

But it gains bonuses for + all skills, no? I also think if you use it in conjunction with another skill, it can become a viable build.

The problem with this is the +1 to all skills raises mana prices, so you might as well go all in on orb of annihilation, except if you have summons like Wolf Companion (which I do and it's a huge boon - more damage done, can't go wrong with that!). The mana cost on OoA, thankfully, doesn't change so going nuclear on that spell doesn't hurt one bit.

MajorCooke wrote:The problem with this is the +1 to all skills raises mana prices, so you might as well go all in on orb of annihilation, except if you have summons like Wolf Companion (which I do and it's a huge boon - more damage done, can't go wrong with that!). The mana cost on OoA, thankfully, doesn't change so going nuclear on that spell doesn't hurt one bit.

can you explain to me how Wolf Companion is a huge boon for OoA?

Well maybe not a huge boon but the relic adds Hunter's Mark, which increases how much damage a marked enemy takes.

Hunter's Mark only applies to physical damage. You would also need the barb passive that converts it to reduce enemy MDR instead, and even then it's a few hundred points of damage at the most.