This bug should exist on both JP and Global servers, as one of the comments that prompted me to look again was actually on the JP Swiki from November. This is not a mistranslation. This also wasn't the first time I had seen something about +10% Enemy HP being worse than originally thought.
I tested on TeLu with Idesigure and Rafoie for maximum status chance. Unfortunately, Voltage turns out to affect burn damage, so the end result in my test was a bit off from 20%. This was also done in Covert Ops Naverius.
Step 11 Rockbear Burn damge: 228,457 (14 voltage)
Step 11 Rockbear +10% Enemy HP Burn Damage: 273,711 (6 voltage)
With the voltage being considered, this is ~20% increase.
The original post on SWiki did similar but with a different class that wouldn't scale ailments as much, and applied the burn with no weapon on. This was done, again, in Covert Ops Naverius.
Step 16 Rockbear Burn Damage: 205,478
Step 16 Rockbear +10% HP Burn Damage: 246,574
Again, a 20% increase in damage, not +10%.
Burn does a percentage of the enemy's life when it ticks, which is why it is used in these tests. I'd imagine you would find the same results with Caterdransa poisoning, but have yet to confirm.
EDIT: Further testing done after Milranduil told me that Bomb damage in Eradication Ops is based on enemy HP. I used the first spawn of mobs in every case here.
Lillipa Eradication Step 11 no mod Spardun A bomb damage: 34,990
Lillipa Eradication Step 11 +10% Enemy HP Spardun A bomb damage: 41,987
Almost exactly 20% increase.
Wopal Eradication Step 26 -20% Enemy HP Turbon bomb damage: 29,441
Wopal Eradication Step 26 +10% Enemy HP Turbon bomb damage: 44,161
29441/0.8 = 36801.25 * 1.2 = 44161.5
Assuming -20% Enemy HP is working as intended, this is a 20% increase compared to what base is.
This confirms that it's not just Covert Ops, but Eradication Ops has the same issue. I think it's safe to say it's likely bugged in every stage type of Divide.
I have screenshots of all testing done, but as to not flood the boards too hard I haven't posted them at the moment.