I feel that this is sorta like a Crawdaunt situation. Marowak can hit really hard, but with its awful speed, mediocre special bulk, poor HP, a small movepool and an abysmal defensive typing, it's going to be fairly easy to outspeed and faint it with a single giga drain, scald or ice beam. But whereas Crawdaunt has aqua jet to get past and usually KO a lot of Pokemon, Marowak does not. Hre are some calcs to show you where I'm coming from:
252 SpA Rotom-F Blizzard vs. 0 HP / 0 SpD Marowak: 372-440 (142.5 - 168.5%) -- guaranteed OHKO
252 SpA Life Orb Frogadier Hydro Pump vs. 0 HP / 0 SpD Marowak: 416-491 (159.3 - 188.1%) -- guaranteed OHKO
252 Atk Choice Band Leafeon Leaf Blade vs. 0 HP / 4 Def Marowak: 360-426 (137.9 - 163.2%) -- guaranteed OHKO (even good physical attacks get him, the HP stat lets him down)
and if you don't like the choice band on that last one, here's the swords dance set:
252 Atk Leafeon Leaf Blade vs. 0 HP / 4 Def Marowak: 240-284 (91.9 - 108.8%) -- 50% chance to OHKO
Now keep in mind Marowak can't kill Leafeon with one attack so it could use to leaf blades or set up a swords dance and kill.
I hope this helps you in your future endeavors.
So Marowak has a very useful long hard bone
I'm sorry. I have the humour of a 10 year old.