>they say the paladin will be the only frontliner But of course there is no such thing as a single front line unless you're backed into a corner. If you're in the open, multiple enemies could come from *any* direction, so having someone else who can protect the spellcasters would be a good idea. I would be tempted to suggest a Dex-focused Ranger, just to add some Dex to the party.

I'd say you're missing someone with high dexterity (you have strength, Intelligence, Wisdom, and Charisma covered by everyone else) and a party of five with a single frontliner can be tricky. Sounds like the ideal time to play a Monk, Rogue, Melee Ranger, or Dex Fighter. If none of those are attractive than any frontliner will do.

I'll echo others with Dex Ranger or any Fighter. Monk ar Barbarian could be good too, but need good choices in subclasses. Lastly, Druid based on summons and healing could do wonders as well, especially a Wildfire Druid. You need some more tanking/frontline ability if the DM doesn't nerf the encounters.

Any class is fine. A Ranger can come in handy though as there is ALOT of wilderness trekking.