The opposing Delibird used Present! Cloyster lost 48.2% of its health!
Starmie used Recover! Starmie restored its HP. The opposing Smeargle used Present! Starmie lost 100% of its health! Starmie fainted!
I disagree, after implementing it on a server and testing it, Present is surprisingly relevant. Most of the Pokemon with STAB Present tend to lack offenses, which Present partly fixes. It hits its targets for something like 25% HP with a 40BP attack (the lowest damage output), and that's Pokemon with very high HP like Vaporeon. Playtests have included Normal-types 3HKOing Acid Armor Vaporeon and Curse Entei (Present ignores stat modifiers) with a 40BP > 80BP > 80BP which isn't too unreasonable especially since they can be pressured into Rest loops, and OHKOing low-ish HP mons like Starmie with a lucky 120BP attack as shown above.
To reiterate, the way it works is the user's secondary type* overrides the target's Defense stat (not stage, stat), which Normal and Flying (which covers most Pokemon with Present) effectively reduce to 1 Defense, the target's secondary type* overrides the user's Level stat (all Special-type indexes are 20 or higher), and then the Attack stat is set to 10, and uses that for the calculation. Which results in potentially ridiculous damage from any Normal-type vs. any secondary Special-type.
High tier Pokemon that Present can maim:
Uber: Mew, Mewtwo, Celebi
OU: Cloyster, Exeggutor, Jolteon, Raikou, Starmie, Suicuine, Umbreon, Tyranitar (resisted), Vaporeon.
BL: Alakazam, Entei, Espeon, Houndoom, Jynx, Kingdra, Lapras, Meganium, Typhlosion
* - Pokemon with one type internally have the same type twice.
It is very practical on mons with 0 offensive presence like Smeargle and Chansey (maybe Snubbull for a low tier desperate for Heal Bell?), and even something with usable offense like Blissey or Miltank has niche use of it to tear specific targets like Raikou or Charm Umbreon (again, Present ignores stat modifiers / screens) to shreds. Heck, I'd argue it could be listed as 'viable' on Normal-types for the Gen 2 teambuilder despite the chance of healing opponents. As for those that lack STAB, Azumarill and Raichu (and their Prevos) have garbage damage and shouldn't ever use it, and Delibird's Present without STAB is somewhat mediocre.
Just in case somebody complains that Blissey/Chansey can't learn both Heal Bell + Present, they actually can via a Smeargle > Snubbull > Chansey chain, but isn't recognized by the teambuilder.
I'll be doing a pull request to implement accurate GSC Present soon.
Edit: Also, as far as I can tell from the disassembly, Present ignores all stat modifiers, so don't expect to sweep with Curse Blissey or have Acid Armor Vaporeon tank any hits from STAB Present. Also, Flying as the attacker's secondary type reduces damage more than I thought, which accounts for Delibird's mediocre damage, and also means Togetic will do less than compared to the other Normal-types.
I've also set up Present on a local damage calc build, will be doing a pull request for that soon. Enjoy some calcs in the mean time:
Blissey Present (80BP) vs. Cloyster: 247-291 (81.5 - 96%) -- 56.4% chance to OHKO after Spikes
Smeargle Present (80BP) vs. Raikou: 227-267 (59.2 - 69.7%) -- guaranteed 2HKO after Leftovers recovery
Blissey Present (120BP) vs. Tyranitar on a critical hit: 368-433 (91.3 - 107.4%) -- 46.2% chance to OHKO
For those worried about it being OP:
Blissey Present (80BP) vs. Snorlax: 43-51 (8.2 - 9.7%) -- possibly the worst move ever
Blissey Present (80BP) vs. Machamp: 43-51 (11.2 - 13.3%) -- possibly the worst move ever
Blissey Present (80BP) vs. Zapdos: 43-51 (11.2 - 13.3%) -- possibly the worst move ever