I think that to decide which faction in HoMM 5 is stronger (if we are talking specifically about strength, and not about which faction you like), it is enough to remember against which Castle you least like to play...

Very progressive approach! I completely agree!

Despite their awesome power, Ents, as usual, peacefully sleep for most of the battle. It is easy to take them out with archers + lightning/ice bolt (with the appropriate ability that forces the target to skip a turn).

But to prevent them from sleeping, you need to take Light Magic and Righteous Vengeance; then they will run! And since they have awesome speed (not initiative!), they run very far away immediately. It is almost impossible to take them out with archers (especially academy archers), because they have an incredibly large number of hit points; I even like it when enemies attack my entrenched Ents instead of killing the archers.
Rakshasa, by the way, have slightly more initiative than Ents; however, if a Rakshasa uses Charge... then they cannot be compared.

Djinn easily bind archers.

but not for long:)

and soon Gargoyles join them. By the way, Gargoyles are disgustingly drawn, but this does not diminish their usefulness. They are practically invulnerable to attack magic - which means they automatically draw enemy units to themselves. So again - they "don't let" us get to the enemy ranks. We stand and shoot at the dummies.

That's true. Although, in general, you can ignore them - they still cannot kill anyone. In fact, Gargoyles work very well for Nazir (who has Fireball) - if the enemy decides to attack and break the flying units and surrounds the Gargoyles, then that's when you need to hit them with a Fireball...

Golems can still be survived - they are at least slow...

Better to say sluggish. And you can survive them without difficulty. Bind them with the same Ents - and all their endless attacks are useless.

Well, mages... that's just awful.:( They will kill a lot of units, and it is not so effective to bind them - they will cast, dogs, Fireball - and also help the "master" with mana.

Mages are actually not that strong. Yes, Fireball is cool. But how many will they cast? No more than 2. And when the mana runs out, it becomes difficult for them to shoot; this is not like Druids.
Rakshasa are cool, no doubt.

Titans, no matter what, are thick and powerful. And also archers and casters... it's a disgrace.

Well, but Titans are not that great. They are not that thick. Their ability is pleasant (casting, that is) - another retaliatory attack:cool: And their shooting is so-so.

In general, in 5, archers are very weakened - the enemy covers the map too quickly.

Well, the coolest are the Necropolis. I really don't understand what the argument is about, because how can you defeat a monster that has twice as many units as you? You can, of course, but for this you need to invent various tricks, hope for luck (like a city left almost undefended)... as you always have to do when you are much weaker than the opponent.
Moreover, the Necropolis has the hero Vlad, who can almost completely restore one of his units in one turn. Of course, there is a solution - to attack individual units. But then you get too many retaliatory attacks.

Added 2 minutes ago
And the Dwarves are kind of lame. They cannot inflict any damage; the fact that no one can inflict damage on them is not an excuse!
Only their runes help them (if the right ones appear; and if the wrong ones appear - goodbye, little guys!)
It's just that it's difficult to take their Castle.