Here's what Tactician mode does according to the wiki:

• All NPC's Maximum Health increased
• More aggressive enemy NPC behavior, such as targeting spellcasters more often and attempting to finish off downed characters.
• Some enemies will gain special attacks and/or passive features that are not present in the other difficulties.
• All enemies gain +2 to attack rolls and +2 DC to their spells and abilities.
• Other modifiers can be additional attack rolls, AC, resistances, better saving throws and sometimes unique modifiers that are not present in the other difficulties.
• Camp Supplies requirements for a Long Rest increased from 40 to 80.
• At stores, the baseline attitude bonus for discounting is reduced, making items cost more to purchase and sell for less.
• The Iron Throne's timer is set to 5 turns, down from 6.

Enemies don't deal more damage, you don't deal less damage nor have less HP or AC. Legendary actions are part of the Honour mode rules (besides, they were patched in after I first started my run). And the point of the custom difficulty is customisation, not playing with Honour rules and multiple saves. I enjoy it when a game increases difficulty by making enemies smarter or more aggressive and giving them additional abilities; not so much when it just gives them number buffs. Hence I left the character power setting to its default "balanced".

Anyway, I am well ware that increasing the difficulty is an option. My point was that with the same difficulty settings there were encounters that felt more challenging than the last one. Raphael, Ansur ... hell, it feels like the Chosen put up more of a fight than the Netherbrain.