This is the Heroic team I used in a recent game of MK Dungeons.
Ignore the point values listed because that only shows their highest values; they all started at Level 1, and collectively they add up to 98 points, which fits nicely into a 100 point team. The fourth member is actually Gatekeeper Bassan, but he apparently doesn't exist in the MT database so I threw in a Standard Bearer as a placeholder (they use the same mold).
This team was designed with an emphasis on ranged attacks, but can still handle a little melee if the need arises.
Bassan (22 points) isn't noted for his strength as a melee attacker, but he does come with the excellent Polearm ability at his first level, which helps to keep enemies at a distance where the rest of the team can pick them apart.
Lady Arowyne (25 points) is the healer of the group and mostly hangs back to patch up the others as they take damage. When the opportunity presents itself she can reach out with Magic Confusion, in the hopes of either turning away a dangerous Mage Spawn, or more simply to move it into a position that makes it easier for the rest of the team to attack. I recently "rediscovered" the ability after realizing that it can't be counterattacked (somehow I'd always missed that last line), which made it much more worthwhile, especially with figures that have a good chance of missing with their attacks.
Sky Heron (29 points) is the thief of the group, but also doubles as the primary ranged attacker until Joram levels up a bit. With help from Joram her three attacks can do two damage to three different enemies at once, which can add up quickly. She gets only a single +2 bonus when disarming traps (thanks to her Nimble), but since the rest of this team is fairly fragile I preferred to have some extra fighting ability rather than a pure (+4) thief.
Joram Hawklord (22 points) starts out as the main support piece and lends his Magic Enhancement to the ladies on the team, but he can also dish out some damage of his own at range. Once he has leveled up twice he gains the powerful Magic Blast ability, which thanks to his 10 range allows him to strike anything within 5 spaces regardless of what may be in between.
As a whole, this team should move through the dungeon at a casual pace. They need to make progress of course to keep up with opponents, but shouldn't move so quickly that they get overwhelmed. Obviously they're meant to stay fairly close together so the biggest threats are likely to come from attacks using Sweep or Flame/Lightning, especially in counterattacks.
Level-ups should be given on an as-needed basis to keep people alive, but if Lady Arowyne is able to keep things under control you should try to push Joram to level three as quickly as possible.