Folks, throwing around random percentages and numbers is not a good thing to do, especially when the stats are directly in front of you.
Let's recap.
We'll include Eldritch Storm also. Those are the measuring sticks we'll work with for the moment. Those are all abilities that are large, end-game AoE attacks that attack both infantry and buildings.
For Eldritch Storm, it does ~110 damage to infantry, knocking them back, or ~1000 damage average to buildings should the Farseer use it on them instead. Radius of 10. 180s recharge, no cost other than research.
Orbital Bombardment does ~110 damage per strike to infantry, ~440 avg dmg. to vehicles and building_low, and is intended to do ~110 dmg/strike to medium and high buildings, but is bugged and does more. It should do ~1500 damage total to those targets. It strikes up to 16 times and each blast is in a radius of 10, and offset from one another both in time and distance. 240s recharge, no cost, but can be disabled by destroying Orbital Relay.
Earthshaker Round does 500-1400 damage to infantry, depending on armor class. It has a radius of 8. Does 1000-1400 to vehicles and buildings. It has 120 range. It costs 200/200, has a 10-second setup time, and is on a fragile, 150/300 platform.
Burna Bomb does ~360-1200 damage to most infantry, 1200-4000 to vehicles, 600-2000 to buildings. It has a radius of 15. It costs 0/100 on a 50/50, potentially invincible platform that can approach from 4 separate targets, takes 6 seconds to detonate, and can be destroyed before detonation if player is aware.
The gold standard here seems to be that the big AoE spells do a bit over 100 damage to infantry and a bit over 1000 damage to vehicles and buildings. IG pays 200/200 for the ability to shoot from 120 range, and has to be Nostradamus to hit anything besides a building. Their platform costs 150/300 and a depot to be fielded in the first place.
Ork, however, pays 0/100 for something that, on complete average, does ~750 damage to infantry, 2500 damage to vehicles, and 1300 damage to buildings, though wildly varying. It's also in a much bigger radius.
The other spells are limited to single entities, aside from the Basilisk. Ork can approach with 4 Doks, though, leaving a player afraid of a bomb in the midst of a skirmish while another Dok sneaks into a base.
The issues:
1) Damage is much much higher relative to other big BOOM abilities.
2) Area of Effect is much much higher relative to big BOOM abilities.
3) Multiple cheap delivery platforms.
4) Said platforms can be invincible
5) Bomb cannot be removed without explosion currently
6) Delay between planting bomb and explosion is only 6 seconds. Due to such a large AoE, 6 seconds may not be enough time to get out of way.
7) Short delay between Bombs
There are several things that can be done.
1: Damage can be reduced to levels comparable to other "BOOM" abilities. ~100-200 damage to infantry, ~1000-ish damage to buildings, big AoE, long recharge time.
2: AoE can be reduced. Perhaps. If damage is lowered, than not so much of an issue.
3: Cost can be increased if damage is still higher than other "BOOM" abilities. This reflects nature of high AoE, multiple delivery platforms, and quick deployment. However, this must be balanced with the probability that the bomb will actually go off.
4: There's the thought of using the Warboss, too. This would have to be coupled with making the bomb so that the Boss can get out of the way before the blast as well as still be useful.
5: Pretty obvious that this one's going to be fixed.
6: Deployment time increased, perhaps through setup time on the Dok as suggested. This could require extra durability on the Bomb so that there's a pretty decent chance it'll still go off.
7: Global timer increased is obvious route, but needs to be balanced with utility of Bomb.
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Again. My thought is that Bomb damage should be brought down to at least that of other "BOOM" abilities (100 inf, 1000 building / vehicle) if it's otherwise fundamentally as is (big AoE, Doks, 0/100). That's reasonable enough.
Warboss is definitely a pathing issue, and Mek's icky too. Weavern makes good points.
Recharge is debatable depending on final damage values.
Detonation time / durability takes fine-tuning. Can't say much there.
Those are the data that we've got on this thing and methods of making it comparable.