Well, that'd the issue at hand: you don't always tell the reader to use Devastate before HS and far as I can tell he in fact always should. The two main quotes I find iffy in the threat/rage section are "This is how your tanking abilities break down in terms of
threat per rage: Revenge > Shield slam > Heroic Strike ~= Devastate" and advising that "If you have improved heroic strike, use HS before devastate." As noted above HS is inferior to Devastate for all talent specks unless I've miscalculated something (well, apart from fudging crit, AP normalisation, glancing blow reduction and so on with rough approximations rather than actually accounting for them...), which would hardly be the first time. I can't see how an assumption of infinite rage would make a difference to theoretical threat/rage to upset this either.
I think the issue might stem from recommending
the TPS sheet as a source for threat/rage values, which makes me think you might have used this to derive your own values. The spreadsheet is a great tool, however it grossly inflates HS's threat/rage for the purposes of comparison with other skills by counting the white damage you would (glances aside) have done regardless as a part of the threat gained from using the skill. If you used the spreadsheet as a source your numbers will be off by about 15-20 threat/rage on HS.
Edit to avoid double posting again: If you want the spreadsheet to accurately model HSs TPR for the purpose of comparing with skills, modifying X6 to read =(V6-V3)/W6 should be all that's needed, I think. Far as I can tell it doesn't even break any of the skill cycle calculations.