I know this system lends itself to all sorts of overpowered multiclass and party compositions tactics, but I was looking for something simpler. What would be the best class for MC to pick to go pure with 1-20, ideally with using the NPC's in their own class as well? I'm not using any mods or respeccing, and it will be played on Challenging.

I don't really want to have to use 'cheese' tactics or metagame to have to get through the game until a build 'clicks' or anything like that. I'm fine not being the 'best' choice, so long as it gets the job done at all levels of the game.

edit: also, if it's possible to do so without lots of buffing, it'd be ideal. It's not really like NWN where you're in 'combat' pretty continuously, so depending on buffs to win simple fights going in and out of map areas wouldn't be ideal.

Best pure class would be vivi, I guess. As to no buffing part... that's really a wrong game for that. Even on lower difficulties.

Yeah, I was afraid of that. Looks like already a long game, and the tedium of constant buffing is a bit of a turn off. From what I played, this was like Storms of Zehir, with constant buff dropping due to zoning. It seems to share the utter lack of AI though, and even less Dispel than that game had, which is weird. I know in other games like Pillars could get by with only using the Priest to cast spells on the 'tough' fights and a decent optimized team handled the trash otherwise.

Vivi does look good though, is there something to do for early game? At a glance it seems to be either resting a lot, or depending on the team to carry the water. Are they able to do that? When I tried using Valerie and Dwarf to tank, but they still got chunked pretty easily.

Vivi has a decent AC ramp. and is perfectly capable for whatever you'd want him to do and there is pretty much nothing one can screw up about Str vivi for challenging. Pretty sure vivi can take on challenging without any feats at all, just by picking mutagen upgrades.

Don't know how big the difference is from normal difficulty, if it's a bit more tricky, or a huge gulf, but once I had some levels under our belts, it was mostly fine to do most location maps with no buffs, or just using good hope from Linzi. Several melees probably helped in my case, because at some point they just chunk everything pretty darn fast. Just Linzi signing helps a lot too. I've missed her when she hasn't been around.

There are long-term buffs with durations like 10 minutes/level, 1 hour/level, or 1 hour (flat) that are simple and painless to use. Stuff like Magic Vestment, Communal Delay Poison, Communal Resist Energy, etc.

Alternatively you can focus on really short-term buffs that are not meant to last longer than one fight but have an enormous impact. Haste, Prayer, and so forth.

It's the 1 minute/level buffs that can be a drag. If you use Extend Spell, you can get those to last long enough to let you clear an entire area (or maybe more if the areas are small). Traveling on the world map will kill your buffs though. Usually. Unless you have something like Extended Magic Vestment.