Let's go through it step by step:
A large number of skeletons can be countered with the Cave Lurker's Killing Blow, but there aren't that many skeletons in the newer versions anymore;
Healing nymphs can be countered by quickly killing Ents or nymphs; the Wasp Swarm is weak, but removing the enchantment doesn't always work;
Draining mana from Imps can be countered by any strong, high-initiative unit (it's better for a Warlock to lose one unit than all their mana, because they won't be able to restore it in battle);
Repairing Gremlins is pointless because it only happens once;
Stalker invisibility is not protected against area-of-effect attacks (Meteor Shower, Fireball, etc.), and the poison loses its effectiveness towards the end of the battle;
Gnomes with their defense are very weak in attack, so they don't make much of a difference;
However, the specializations of Goblins and Peasants (which can be left unupgraded and kept with Elaine in the castle) cannot be countered. You can't call them the best, but I think they are much more useful... the rest don't matter.
But as a fan of the High Elves, I can't help but defend the Nymphs.
The trees will live until the very end and die last, as they have the lowest initiative among the troops of the Forest faction. As for health and hit points, no comment.
It's also not easy to quickly kill Nymphs, especially when Dragons that moved first are flying around, Dancing Unicorns burst into your ranks, blinding everyone, and I won't even mention Druids and Archers.
Under these circumstances, would anyone want to harm the little, kind Nymphs?!
Hunter! Just because it "activates" invisibility for 3 turns! This really saves them from unnecessary losses! And the small increase is compensated by their strength.
