Gems: Water (HP) vs Earth (Def)

[Undefined]

All the guides/advice I've read recommend HP over Def. One of them says that HP is better for dungeons and Def is better for UBv4s, but none of this is ever explained why.

My question is in regards to dungeons, so I'm wondering, why does HP get favored over Def?

[luizpedronovak]

Not every damage comes from ATKxDEF. Speed damage for example: when the attacker (either the monster or the pet) has a large speed, the target will receive some speed damage. This bypass defense, so having a high DEF is useless. Having a high HP will allow you to tank both damage from direct attacks as damage from speed. Same thing for traps, venom, etc.

In the end, what you want is to survive; HP will help to survive from every type of damage, def will help in direct attacks. So, HP is more useful. But ideally, you want both.

[n00bdragon]

As the game has evolved there have been a lot more sources of damage that completely ignore defense. Defense is never pointless, it's very nice to have in many later fights where enemies can dish out some serious damage to even your tankiest pets, but things like speed damage (which becomes a substantial source of damage in some fights), room events that deal direct damage, poisons, etc. All of these things take a toll on your HP directly.

[muljostpho]

The reasoning I've seen explained on that before this was about intercepted damage. It's one thing when the enemy specifically targets the defender directly. As the intended target, their own defense and elemental stats factor into the damage calculation. But when the defender steps into the way of an attack that was meant for another pet, it's that other pet's stats which are used in the calculation, and the defender just absorbs a share of that damage. (This was explained this way before D4 or towers or a lot of the post-D3 special bosses were added to the game, and speed damage was thought of as weak and irrelevant.)

Where UBv4s are concerned, as you can see in the calculations explained at the bottom of the page brought up by the "show stats" button, the distinction is that HP for those fights is based on (HP of all pets)^0.4 while defense for those fights is based on (defense of defenders) + (defense of others)/10. A root function vs basic addition. Every extra point of defense you can squeeze onto those defenders will be equally relevant while each extra point of HP will be a little bit weaker than the previous one.

[ShinkuTear]

Supporters healing has 2 main pieces, a flat value and a % of the targets Max HP. The more Max HP they have, the bigger the actual amount of the % portion will be. This is ultimately the key in why Max HP is favored for so long.

The majority of damage Defenders take before D4 dungeons will be from using their weaker defensive ability (where the Defenders damage taken is based on the targets defenses instead of their own), from Speed Damage (which IIRC is Half of the Speed gap between attacker and victim), and from special enemies like Mimics who have significant raw offense.

As a result, most of the damage Defenders take is easier to mitigate with More Max HP to have more leeway to endure it all and heal back up, rather than more DEF that only helps endure some of it.

Defense is still a useful stat for survival, to the point that Magic Pots are better Tier 3 weapons for Defenders than the Titanium Swords (which waste more than half of their stat budget on ATK). When it comes to Gems, dungeon durability tends to be improved more with adding to Max HP first, and Defenders specifically tend to benefit from having 2 or even 3 HP gems.

UBv4 however, specifically goes and makes clear that Defense is still a very important stat. If your assigned pets are all approximately in line with each other in DL/CL/Gear, I have found that fights can be won in a single shot so long as my Defense was equal or greater to the v4s Attack. UBv4, your HP is also capped at 100x the Clones you assign... but your Defense is not capped.

[Xelos]

One thing to note is the damage formula.
TargetDefMulti = 1 - TargetDefence / (TargetDefence+200)
So if you have low defence doubling it won't make you take half the damage.

Speed damage is not a big deal before D4. If I remember correctly, it is only around 10% of total damage you take. So def will still make huge difference.

Gems give flat percentage boost to stat. This means that, the lower your stat boost from equipment is, the better the gem for this stat will be. Going from 200%->240% hp may give you less survivability, then going from 100%-140% def.

[Undefined]

Thanks for the help everyone, makes a lot of sense!