When they ran this promotion last year, I averaged a 2.6X point multiplier. If they kept the same algorithm of switching between 2x, 3x, 4x and 5x points as you play as last year, then a 2.6X mulitipler would be a comp rate of 0.33 x 2.6 = .86%. Last year the base comp rate was 0.45% which yielded a muliplier of .45 x 2.6 = 1.17%. The current 0.86% is not as good as double points at Mohegan Sun (1.33% on April 13), but I'll probably play Foxwoods Xtreme Dreampoints anyway.
My suggestion to Foxwoods that if they cut the comp rate further to 0.0%, they could offer 1000X point multiplier every day, and still make money on the promotional value of a multipoint day;-)