These days, Rampart is my favorite Castle (although before, when I was just starting to play for money (student money, that is)), I constantly used it with my Necromancers...
Since I play on an XL map with 200% difficulty, I choose Ivora (he always has Elves at the beginning), and this greatly helps at the start of the game...
By the way, at maximum difficulty, the winner is not the one with the best attack/defense, but the one who can develop quickly at the beginning and build a Castle and creatures, and clear the map...probably no one except Great Elves (and, perhaps, upgraded Archers from Humans) can do this with maximum efficiency...Eye of the Storm? - it's hard to build without resources...Lizards? - they are quite weak as ranged attackers at the beginning...Orcs and Magogs - the same...
Elves can be upgraded in the first week; all you need is wood (and a little money)...this pays off quickly...))))
So, you can only compare individual creatures of Castles on small or densely populated maps with a lot of action...on XL, the approach should be different in principle...
The heroes in Rampart are excellent (there's no point in listing them - they've already been mentioned)...diplomacy appears very often (with Ivora, it's almost always)...and although my friend and I play WITHOUT heroes with diplomacy (for balance), nothing prevents you from playing if this very useful skill appears during the game...))...I like Rampart because it is very balanced (there are no obvious weaknesses)...and its resource spawn is usually very good...many stone gardens, mills, etc., which makes the hero's life easier))))
Some people think that Pegasi are weak (they have few hit points)...but, comrades, a +10 bonus, high flying speed, decent damage, and a special ability in the form of increasing the enemy's mana cost are not given easily)))).
Slow Dendroids?...well, what do you need the Tactics skill for? (it appears quite often with Rangers)...in general, I think Rangers are definitely better than Druids: excellent defense, skills including water and earth appear very often, as do diplomacy and luck...all this combined gives you a well-balanced hero who can play on equal terms (or even better) against mages, and against fighters...and even against fighter-mages))))...I don't really understand the special reverence for Necromancers, as if they are practically an invincible option in skilled hands...comrades!!! on XL and 200% difficulty, even hordes of skeletons will not be a big obstacle for a properly developed Rampart!!!