Too bad then, looks like it bugged for you...
I'm not sure how exp splitting works, but I'm certain dead people receive LESS exp, so try to keep them alive. Besides, you should never bring level 30 guys around: waste of exp. The max you should ever level them is about level 24, unless you're leveling them to the max in order to graduate them at the end of the month for the 50% bonus. 4 x level 24 chars can win you tournaments easy.
I'm not sure how points are awarded for errand missions, but in general I see myself getting less for errands of the same rating compared to hunts, even if I try to meet the errand criteria e.g. sending my best sorceress when they ask for them, and sending my best gunslingers when they wanted chars with high dex. So try to go for hunts whenever possible.
Agree that 4 star hunts > 5 star hunts due to larger number of enemies. The ideal ones are wolves and barbarians since they're not ranged, which allows you to abuse the pathing AI to the max. Always have at least one ranged char, once you enter the hunt run to a safe spot beside any bit of water one "square" across. Disable assistance (press W), send one guy to lure enemies to the spot across the water from the rest of your party. Quickly select another member of the party and press shift to teleport him/her over. Now the enemies will stupidly be stuck across the river, giving the ranged guy free shots. Heck, using this tactic you can beat the 4-star wolf hunt with 4 level 1 guys, easy peasy. However, the map is randomly generated so sometimes you will start off being surrounded by 20 wolves with no suitable spot of water nearby to abuse, and you will thus lose if you only bring low level guys, but this does not occur often.
For tournaments, disable assistance IMMEDIATELY once you start, and manually select each guy to focus on the ranged enemies to take them out first since they have less HP. They aren't actually very hard.