Balance in Heroes 5.

If I remember correctly, the main schools of magic for the Academics are Summoning and Light, so you can only get Armageddon with a library, and even then, if you're lucky. Well, okay, you got lucky and have Armageddon.

Here are a couple of options on how to defeat the Elf:
1) The simplest option is for the Archers to be eliminated before the Academy hero's turn with Armageddon. By the beginning of the 3rd week, Ossir will have 35-40 of them, and they can definitely take out 40 Gargoyles if they're lucky (which the Elves upgrade early and works often) or the Gargoyles are in Cursed and the ability triggers (and if a lucky attack from a Cursed enemy happens... it's devastating).
2) Option number two - Unique units. We build Unique units in the 2nd week (sometimes even in the 1st, if the city is already somewhat built up at the beginning) and place them on the battlefield next to other units. With the Magic Resistance ability (Luck branch), the chance that Armageddon will be deflected is approximately 45% (30% from the Unique units and 15% from the ability). Then, follow option number one.
3) Anti-Magic :) - why shouldn't the Elf build a guild to at least level 4 if the Academic has built it to level 5 (the chance of getting it is 50%)? We cast Anti-Magic on the same Archers and that's it.
There are other options, but I won't list them all. That's enough for now.
Regarding the Training for Heven - the statement that it has been nerfed is debatable. Yes, now you can train a maximum of 20 units per week... but the price... is twice as low, which means many, many more Inquisitors and Paladins instead of a bunch of Crossbowmen. It's simply a transition from quantity to quality. The Necromancers have the same situation, although they now depend heavily on neutral creatures.