On the long term you want a Knight-Mage with
Minoan. She gives a 15% Attack bonus and 10% damage reduction to Knights if a Mage is pressent (Mages also get 12% Attack bonus) so is better to use Liam. There is also a Knight that gives attack bonus to Archers but only gives damage reduction to knights so I wouldn't put Leaho in with her. Maybe is better to find kizuna debuff rather than putting someone weak in a team.
Liam, while not bad, is not one of the better options for a Minoa team, specially with Leaho.
Ideally, you want 2 Minoas on the field, as the auras stack. From there, you can choose to go knight- (higher aura buff) or mage-heavy (higher damage output, better aoe).
2xMinoa-KnightA-Cleric/KnightB-Mage is a standard
knight-heavy comp.
If you go with 2 knights instead of a cleric, you can field Leaho+a poisoner, thus getting 3 status effects through skills/attacks - I'm thinking of Vespa here, since I can't think of any other knight that can poison enemies. However Vespa buffs ranged attackers and you only have one. You are also missing healing, but you might be able to wave heal through kizunas.
2xMinoa-MageA-Cleric/MageB-MageC is a standard
mage-heavy comp.
Assuming Liam is C you can field 2 other mages, ideally Alphim and Shauna (healing). However, since few mages have strong synergy with debuff teams, Liam might as well be any other mage.
So to make use out of a debuffing ability in a Minoa team you have to go knight-heavy and probably use Vespa for the poison (you went knights to make use of the extra 3% and now you are wasting a 6% buff on a single ranged character).
Essentially, when using Leaho she is always the core because she needs very specific conditions to be met in order to shine, and fielding 2 of her is actually pretty good. To that extent, since she provides blind you want arcana who can slow and poison. These are usually gunners/archers, and they usually buff themselves further through inflicting debuffs (much like Liam and Sasha's +50%atk against slowed enemies). Keeping in mind the continent of sins should release a bit after Minoa, and that the tavern is full of debuff-inflicting and self-buffing gunners, I wouldn't really mix a Minoa/Leaho team unless I need knockbacks or don't have enough gunners.
TL;DR: Leaho works towards debuffing enemies with 3 ailments, and Minoa doesn't even care about ailments because she is that good, so they sometimes conflict and, while they can be used together, you might be missing the best of both worlds.
Is Bliza actually good? I got her and didn't think much of her but apparently her poison Kizuna is strong.
Her Kizuna is quite good, I actually use it every now and then in jpCC when I don't want to risk poisoning allies and don't need poison on demand, but that aside... Well, she can craft bows.