I think it's the other way around. The SK sucks in classic and kunark. The chanter can do most of the stuff. The SK becomes important starting in Velious.
How can the best 3 box not start with the best 2 box? Chanter/cleric dominates for classic/kunark/velious. The only thing that gimps it is oh shit moments when charm breaks after kunark. SK solves this.
Chanter/cleric can do quite a lot that your trios cannot do. Charm is OP. Chanter Mes is OP. Bard just is not a good enough replacement. Even if you do not charm with the chanter, the CC is absurd and it's nearly impossible to die when everything is mezzable. It's hard to overwhelm a chanter/cleric. You throw a few adds into those other trios and if you make it out alive, you're cutting it close and draining all your mana because you can't just drop 50 second mezzes on everything.
If you're trying to plan for beyond PoP, well that doesn't make that much sense. Play a trio that's going to dominate for the first 3 expansions and switch after that if you're still playing.
sk/shm/bard
mnk/shm/bard
Thinking about clearing any real camp in classic/kunark with either of those trios just does not sound efficient or fast or fun.
If you're just banking on always inviting a chanter to do that work for you, then it's fine. But, if you like being the most important 3 roles of a group, and just adding 3 random shitter DPS, I recommend chanter/cleric + tank.
I'm not dissing on you having favorites over others, but maybe you should clarify if you mean the best or if you just mean what you're deciding between. Either is fine... but you know how powerful chanter/cleric is for the first 3 expansions, so obviously the best trio should start with those 2. If we are being realistic.
Again, it's totally fine if you just prefer not to play chanter/cleric. But, it is the absolute best combination of 2 classes in terms of power and efficiency.