Agreed, but my situation was that both the Fortress and Conclave had the same essence-tile-yield.
I've also had the plan to make Commander Henchmen but never got that far. I need to up the game-difficulty as I wipe the mobs and AI too quickly otherwise.
And as I wrote in another thread, I found the below combination of Henchmen deadly together with a healing Mage with 1-turn cast Titan's breath (knocks all non-large or non-mounted enemies prone).
Sovereign Henchmen #1; Defender with +10% Xp to army, +25% Xp and +3 Defense to army. Traits; +10/15 Hp (and Plate), bee-line over Stun to +5/10/15 Spell resistance to army.
Sovereign Henchmen #2; Mage with +10% Xp to army, +25% Xp and Life. Traits; Life 2 and Compassion (+50% Healing), +Army heal/season, First Aid, Summon Whisp and Lightbringer - and after that aim for +1 Casting time (for 1 turn Fireball from Annointed by Fire).
Sovereign #Henchmen 3; Warrior with +10% Xp to army, +25% Xp and +3 Defense to army. Traits; +3/4/5 Attack, +10 Hp, Blade Rush, Reap III and Bloodthirsty.
This army is complemented by your best troops and can win over deadly/epic monsters. Dark mage's spells (drain life from all troops) can be counterspelled by both the Sov and Mage-Henchman. While against prone-immune enemies or magic immune foes, it's only a matter of surviving the initial damage (low Hp-troops will have to hang back for a while).
So when designing a Commander Henchman I agree it's good to give it +1 level from traits or Fortress. But when it comes to fighting Henchmen (that are going to level high together with the Sov) I think the +25% Xp and +10%-army Xp traits are better. And I will actively try to make the Henchmen early (or at least queue them in a cityproduction until the city got necessary buffs and Charms and Leather armor is researched) so that my fame is not used up by the second Champ.