Orcs have no magic. Warcries.

Secondly, a couple of goblins (split into stacks of one and used to support the centaurs) won't make much of a difference, especially against fast-moving units (particularly large ones). I won't even mention slow-moving neutral creatures – they don't even reach the battlefield.
As for shamans... stealing magic is only one of three (or so) effects.

The thing is, the chance of success isn't high, especially when fighting a powerful mage. And the risk that the shamans might absorb some kind of berserk spell and attack the centaurs hiding in the rear is not good. But when fighting an enchanter or a light mage, there is practically no risk. Unless, of course, they cast Divine Intervention, Magic Bolt, or Swarm of Bees.

Warlords are really useful when you face armored units; that's when centaurs start to struggle.

Not just armored units. There's also the first level of Gnomish units and Alt-skeletons – they all cause trouble. And even warlords won't help here, because by that time, there won't be many of them left. In this case, I would rely on combat centaurs, as they don't suffer a penalty for melee combat.

Honestly, I haven't used silence spells in a long time, but if, for example, the opponent's magic is obvious and a silence spell is available, why not take it?

In reality, only the Chaos Silence spell is truly effective. And you can do something against Darkness. The other silence spells are learned not for the sake of silencing magic, but for additional perks, such as Secrets of Light and Return to Void.

By the way, I personally don't really like War Cry, but you still have to use it somehow, right? Damage + units of fury is still better than just units of fury (from a combined War Cry).

Why not? It's perfect for boosting the fury of a key stack if it's just a little short of the next level. Frightful Howl is also a powerful ability, especially when it forces a unit on the opposite side of the battlefield, under the effect of fear, to run towards our lines and, at the same time, be pushed to the end of the turn order. And Battle Cry is a real terror for all enemies. But, as I've noticed, it appears less often than War Cry, or maybe I'm just unlucky.