There’s a lot of “advice” to promote all your heroes to Level 20 for the All Hero bonuses, which IMO is bad advice:
Because I consider Hero Medals to be the most important resource in the game; and I think it’s not worth delaying progress on your main heroes (where you’d need 40 medals to get from 29 to 30) by spending 30 to get a hero you don’t intend to play with to Level 20, unless the bonus is really good
The bonuses are not as good as they appear to be - e.g. +5% against Ground Enemies won’t increase your damage against Ground enemies x1.05 because
- The bonus doesn’t apply to Gear Damage
- The bonus adds on (not multiplies on) to any attack bonuses you have from the BattlePass, Elemental Bonus for Event/Castle, Tournament Bonus, etc. So for example if you have +12% Attack from the Battle Pass and 30% from the element, your weapon damage is already boosted 42%. Another 5% on that (i.e. 47%) is only a 3.5% gain (i.e. 1.47/1.42)
- It won’t increase the damage done by perks that depend on Loadout Attack - Zap, Fire / Poison / Flamethrower, and Death Perks (other than Death Shrapnel, which does).
- It also won’t improve damage by Mortis’ Plague Cloud, Dr. Toxic’s Venom, and Fursus’ Iceplosion, although this is not a big deal
For all of the attack/attack speed bonuses, you can see how much of an improvement you will get with it using the Damage Simulator; compare that by using the Hero Stat Simulator to see what Loadout Attack you’d get if you used the medals to promote a hero you play with, and plug that back in the Damage Simulator to see what that would get you
That said, this is what I think of each of the Level 20 bonuses:
- Miasma, Attack +100. This is the best of the lot and is definitely worth spending 30 Medals on even if you are not going to play Miasma (although she will probably be the main Poison hero for most players)
- Mr. Autofire, Dodge +5%. This is really useful, because it ~doubles your chances of dodging (base dodge chance is ~5%) from 1 in 20 hits to 1 in 10 hits. You probably will get Mr. Autofire to 20 on your way to unlocking other heroes anyway
- Jackpot, Dodge +5%. If you unlock Jackbot you would probably level him up to at least 20 because he’s the best Farming hero anyway. This can take your dodging chances to ~1 in 6 hits. I would recommend that the decision to upgrade him further (provided you can spare the medals) be based on how strong you need him to be to get 15 proc’s at your highest unlocked world than trying to get an extra 5% dodge chance
- Shiver: +120 Damage to Melee: This is very handy if you use a fast gun (Autogun / Looper) so I would suggest to take it. Less useful with slow guns
- Firebug +100 Damage to Ground: This is very handy if you use a fast gun (Autogun / Looper) so I would suggest to take it. Less useful with slow guns
- Surefire: Critical Damage +10%: This means your shots do x2.10 damage when they crit, rather than x2.00, so the actual improvement is 5% (2.10/2.00). And that only applies when the shots crit, which I’d guesstimate to be 10% of the time at best (improved by Critical Chance perks). But if using a fast gun this is probably still better than the next tier of bonuses
- Blazia +5% Ground / Armorita +5% Ground / Scorcher +5% Flying / Hocus Focus +10% Flying / S.I.M.O +12% Ground: Because of the way Gear Damage is calculated, this is more useful for slow guns (e.g. Laser Rifle or Devastator) than Fast Guns (Autogun, Looper). So if you use a slow gun (which I don’t recommend because of Hero Passive - Weapon Interactions and Weapon - Perk interactions) these are helpful. Of these S.I.M.O.‘s and Hocus’ is the strongest, and might be worthwhile even if using a fast gun.
- Sanguina Critical Damage +5%, Hecate Critical Damage +3%: Similar to Surefire, but the magnitude is much less, hence ranks lower. However, if you have a hero with the Sniper skill (Blazia, Firebug, Miasma, Hocus Focus) at a high level, this will increase in utility.
- Dr. Toxic’s and Prospero’s Healing +10%. This can help you survive a little longer, because you heal a little bit more from Health Kits and Perk rolls, but I would not consider it worth 30 medals
- Frostina’s Health +5% / Arctor’s Health +6% / Ignus Health +300 / Fursus Health +200: The extra health can help you survive a little longer, but again I would not consider it worth 30 medals.
- Mortis’ Damage Resistance +3%: This too can help you survive a little longer (but not much, since 3% of damage saved isn’t worth much, especially considering how damage ramps up during the course of a run), but again not worth 30 medals
And the Level 50 bonuses:
Once you reach level 50 and promote your main heroes, you will have the chance to promote some others for bonuses while you grind your way to Level 60 (which is when you’d next need medals for your main heroes). This is my ranking of the bonuses:
- Fursus (Attack +125), Miasma (Attack +100), Surefire (Attack +3%): Again, improving attack is the best; whether the flat boost or percentage boost is better will depend on your stats
- Firebug (Attack speed +2%): Almost as good as the attack, I rate it slightly lower only because the way it stacks with Nimble Hands (which you will have at a decent level by now) and the Speed bonuses in the BattlePass. It also won’t increase the effect of Death perks but by now you probably don’t take them except as a last resort anyway
- Jackbot, Mr. Autofire (Dodge +5%): These are good to help the transition from Ninja to Necro (see Best Armour).
- Prospero (Melee +150) > Shiver (Melee +120) > Arctor (Ground +100), Armorita (Ground +100) - very useful if you use a fast gun (however, see note below)
- Mortis (Critical Chance +5%), Hecate (Critical Damage +3%), Hocus (Critical Damage +5%) - I’m not sure how to evaluate the value of Critical Chance vs. Critical Damage. For heroes with the Sniper skill at a high level, Critical Damage becomes slightly more attractive and Critical chance is less useful
- S.I.M.O. (Ground +12%) > Blazia (Ground +5%), Scorcher (Flying +5%), Sanguina (5%) - these won’t add much if you use a fast gun, check the damage simulator if you are using a slow gun. (see note below)
- Dr. Toxic (Healing +10%), Frostina (Health +5%), Ignus (Health + 300): By the time you can consider this, you should be playing Master or GrandMaster League in the tournament and reaching 100+ in the Endless runs; the extra health/healing are not going to make much of a difference.
Note on fixed bonuses (e.g. Ground +100) vs. relative (e.g. Ground +5%):
When you are at Level 20, when using a fast gun, the benefit of the fixed bonus would be more impactful than the relative. However, the stronger you get (hero base attack and weapon attack), the more useful the relative bonuses become, and at some point they will add more to your dps than the fixed ones. When you get to Level 50, use the damage simulator to see which bonus is better - e.g. while I’ve ranked the Level 50 fixed bonuses higher than the relative ones, it may actually be the other way around (especially for the stronger ones like S.I.M.O.'s)