Stick with 2 hp to sever a tentacle, like the original text?
Suggested constrict damage? The giant octopi has an odd amount, based on its other attacks. Downsizing that yields 1d10+Str.
Either this, or I guess we could do 4 hp/tentacle with 2 to the octopus, as Cleon suggests.So 2 hp/tentacle, but no damage to the octopus,
and constrict damage equals 1d2+1?
Giving it some thought, I'm alright with the 1d6 constriction.
My thought is that 1d6 would just be the constrict value, as a reasonable average over numbers of tentacles from the earlier version.

(Dungeons & Dragons)
Rulebook featuring "high magic" options, including a host of new spells.