Yeah, traditional wisdom with D&D parties is similar to WOW wisdom.
You need a Tank (Fighter/Barbarian/Cleric) who can soak up damage and deliver solid, sustainable harm to the enemy.
You need a Divine Magic user (Cleric/Paladin/Druid) who can deliver buffs and heals to keep the party going.
You need an Arcane Magic user (Sorceror/Bard/Wizard) who can break enemy spells and bring out the big guns when needed.
And you need a Specialist (Rogue/Bard) who can multitask into a number of talents depending on the situation.
Once you have those basic four, you can then start doubling up to suit the encounter. Rangers can serve as additional tanks, or additional magic users. You can have two specialists, if you're in a situation that requires precise skills. You can have Paladins double up as secondary healers or tanks.
So whenever I DM I look for the four pillars: TANK, HEALER, MAGE, SPECIALIST. Then I look for the 6 ABILITIES. Do we have someone with high charisma? Someone with high Intelligence? And so forth. As long as all the bases are covered, the party should function well.
Also, here's the direct link to the campaign. This will take you to the training area where you can play around with the system. I'll be finding icons for you all shortly.
https://app.roll20.net/join/107153/dp-6WA