As hard as it can get, it sympathizes teamwork with three vikings to cooperate with each other to defeat the obstacles..
Erik is the agile person, running fastly, and the only one who is capable of jumping. And he can smash through some walls (even enemies) with his helmet, if required.
Baleog is your true viking fighter, using his sword and his bow, is perfectly capable of dealing damage from a range or melee. The bow is also useful to activate switches, which could not be turned on otherwise.
Olaf is your protection, shielding you from harm. If needed, he can also use it as a stepping stone, so Erik can jump to higher areas, which would not be possible otherwise. Teamwork is the key.
Erik, while agile and fast, is not truly capable of dealing with (more) enemies (or other annoyances, such as hostile projectiles) on his own. Erik's most notable skill is to being able to jump. Good skills indeed, but not enough to deal with the challenge alone.
Baleog, while strong as steel, would still not be able to do everything by his own. He could kill the enemies all alone, but some protection for him wouldn't hurt, though, since he seems to lack protective skills.
Olaf, while very protective also has a drawback. If attacked posteriorly, you will be damaged. Also, Olaf is great at slanting with his shield. That means you're not falling if you've jumped out from somewhere high, but will safely arrive at the bottom without dying.
Overall:
Erik-agile puzzle solver
Baleog-tough fighter
Olaf-pudgy guardian
By mixing their skills they are capable of doing things that otherwise would not be possible, and there you have it. This was the game that taught me everything about teamwork. I appreciate it.