Single models (heroes, monsters, Hellcannons) and damage spells are much weaker at Ultra unit size, much stronger at Small

[Gopblin]

This seems to apply to all units that don't get more models with unit scale (e.g. heroes, Hellcannons/tanks/Luminarks, monsters) - damage doesn't scale well with size.
For an especially sad example, try a ranged hero like the Dwarf's Engineer.
On Small unit size, his rifle can do ~40% damage to an Exalted Hero while the latter is running up to curbstomp the Engi.
On Ultra size, Engineer does less than 10% damage.
This seriously limits the usefulness of a lot of units on Ultra (and seriously increases it on Small), and affects balance (i.e. Hellcannons are great units on Small unit size, and underwhelming at Ultra).
Solution: single-model damage should be scaled when unit size is increased, just like HP is. As it is, no one in their right mind uses Engis in MP, for example (most hosts seem to use Ultra unit size).

* In case some1 doesn't know, unit scale is adjusted, counter-intuitively, through Graphics Options=>Advanced, and goes from 40 basic infantry per unit, to 160.

====

Magic scales a bit better, but not enough to make magic really worth using on Ultra unit size (in MP of course, cause in SP you can abuse AI/mechanics all day long).
For example, playing as Vampire Counts, you can pick up Vampires on Hellsteeds for 1500 points, which are really expensive but possess two of the best damage spells in the game: Spirit Leech (single target damage) and Fate of Bruja (unit damage). Of course, Vampires will only be able to cast these spells a few times a game - due to combination of low mana, spellcasts being interrupted, being killed by cannons etc., or not enough time to micro spellcasting.

At small unit size, Spirit Leech oneshots a hero (and half-healths a Legendary Lord), while Fate of Bruja wipes out a unit, making Vampire a very worthy buy even if they manage to get off 1-2 spellcasts.

At Ultra unit size, Spirit Leech/Fate of Bruja only do about 40% damage to hero/unit respectively, meaning one needs to bring 4500 points of Vampires to oneshot something worth about 1000 (and then Vampires just go to being crappy heroes, because it's unlikely there will be enough mana for them to cast 3 more spells).

The same logic applies e.g. for Empire's Witchhunters, which have an "Accuse" damage ability with essentially exact same stats as Spirit Leech - oneshots Exalted Heroes at Small unit size and does about 45% damage on Ultra size. Since Witchhunters are mostly useless except for that ability, people don't use em much in MP.

Solution: devs need to fix the goddam scaling, so that spells are somewhat less powerful at Small and somewhat more powerful on Large.

[Dalgaard]

Thank you for the insight, this is very true.

[Gopblin]

Another good example: Arachnarok spiders are considered weaker then Demigryphs... But are they really?

Turns out, at Small unit size, a spidey absolutely wipes the floor with ChickenKnights, winning every time with not that much HP loss. At Ultra, yeah, Demigryphs always win, because they have like 2.5 times more DPS due to having more models, while the spider DPS stays the same.

At the same time, don't think that Small unit size battles would be dominated by monsters: Arty, missile troops, and spells are the name of the game. With such low HP on every unit, the battle is usually decided before melee is joined. Heck, on Small, a single Hellcannon hit can kill 2/3 of an elite infantry unit, and aforementioned "instakill" spells abound.

[Spitjaw]

Miscast damage also does not scale properly with unit size, on Small a miscast spell can oneshot your Hero spellcaster.
Quite hilarious!