I play allot of D&D stuff so im used to the cruel dice gods but this is absurd, i've had trolls pass will save's 3 times in a row against a 19 DC while my own character's rarely roll over a 10 and i recently had one of the most bs fights in my life against two bugbears that just defeated my entire party, the whole fight they were rolling high and hitting while my own guys were rolling 5's, and Tasha's laughter and deep slumber got resisted 5 times. besides that they always seem to see my invisible rogue once the fight starts. (i like to keep her in back ready to backstab mages once they start casting.)

This may help

http://www.co8.org/forum/showthread.php?t=4210

The thing about randomness is that it's random. Given a large enough sample size, the unlikely becomes practically certain. Also, don't apply tabletop sensibilities to ToEE; the encounters in CRPG's are typically way above level-appropriate guidelines, and ToEE is on the extreme end of CRPG's to begin with.

I'm also unsurprised Tasha's Laughter failed. It has a -4 save penalty if the enemy is a different race than you. If that Bugbear has the iron will feat, then even the highest possible DC will only have a 50/50 chance of success. At those odds, streaks of success or failure will be relatively common.