The tarrasque has two answers to that tactic.Hell, if that's your issue, halflings break the game here. It's got a WIS bonus of +0, so if you give a SINGLE 1st-level dex-focused Archer fighter with training in Stealth a SINGLE magic bow, it can eventually plink T into the negatives as well by run-and-hide-and-snipe-and-run-again. Range matters less with this strategy, so give 'im a sling, and T will literally never know what hit it.![]()
One is to ready an attack for when the halfling breaks cover. This is the standard response for any monster facing a move-attack-move sniper.
The other is that "Siege Monster" ability. What exactly is the halfling hiding behind, again?