Tactics for Rampart.

1. The specialization in Defense isn't exclusive to the Swamp; for example, Mephala in the Rampart has it too. And the Rampart is better than the Swamp again because of its magic, and the creatures there are stronger.
2. The problem is that you need to capture a Castle first. When playing against the AI, this might not be a big deal (although anything can happen), but when playing against humans, it's quite difficult to do without decent magic, which the Swamp Castle doesn't have as much of, just like the Stronghold.

Well, you know, starting with the Swamp is a good idea! Build a Wyvern, and half the map is yours ;) That's one thing.
Secondly, the creatures in the Swamp have special abilities, so saying they are weaker is incorrect.
And finally, thirdly, you usually only use magic up to level 1-2 when playing against humans. You simply don't have time to build more. And if you do, you'll definitely have captured a second Castle by then!
And lastly, why does the Swamp need magic higher than level 3? At level 3, there's Teleport for 3 mana (and the Swamp gets a lot of Water, which is great for this!). Teleport Hydras into the thick of the enemy, and that's it =)) It's that simple!!!

P.S. I love the Swamp!