The Gremlin Nob is an Elite enemy found primarily in Act 1. However, one also appears in Act 2's ColosseumEvent alongside a Taskmaster, provided the player opts to fight. The enemy may seem to have low damage values for an elite, but the Anger buff it grants itself combined with the Skull Bash's applied Vulnerable make for a tough fight for most decks.
With the exception of the first turn, where it has yet to apply Enrage, playing Skills will make the Gremlin Nob much more threatening. Since most Block-granting cards are also Skills, it can be worth more to not play them and take the damage instead. Before using a Skill to mitigate damage, consider how much longer the fight might take.
With the Ironclad's Basic deck, the fight is about being as aggressive as possible until the very end. Use Bash to apply Vulnerable as much as possible, and play every Strike attack you're dealt. When you feel the Nob will only have one turn left to live, it can be beneficial to play a Defend versus a Skull Bash. Burning Blood will absorb some of the impact of the fight at the end.
With the Silent's Basic deck, the fight becomes more painful. The objective, however, does not change. Neutralize Helps to mitigate some of the damage. Taking 4 or 10 damage should be much more manageable. Otherwise, lay in with Strikes whenever possible.
With the Defect's Basic deck the fight plays out similar to the Silent. Despite the strength gain it may be worth it to cast Zap early in the fight (especially if you traded away your starting relic) and Dualcast late in the fight. Dualcast often lets you finish him off a whole turn earlier, making the strength gain irrelevant.
With the Watcher's Basic deck, focus on maintaining aggression and play strong offensive cards. It is usually worth to take damage as the Watcher's style of gameplay can deal excessive amounts of damage in a single turn. Playing cards which enable Wrath or Divinity such as Eruption or Blasphemy to deal a large amount of burst damage can easily finish off the Gremlin Nob.
If the player is fighting the Gremlin Nob in the Colosseum event, it is probably better to kill the Gremlin Nob before the Taskmaster; the Gremlin Nob will continue to gain Strength when you play Skills.