As mentioned before 30 weaker WS is more damage than 20 stronger, but specifically for a fight like mboze that's also 50% more TP fed.
Except...you're adding a shitload of auto-attacks for your 20 WS so...it's not like 50% more TP fed.
Let's say it takes you 10 hits to get from WS to 1k TP and 20 hits to get from WS to 2k.
If you do 30 WS at 1k TP that's 300 auto-attacks and 30 WS
If you do 20 WS at 2k TP that's 400 auto-attacks and 20 WS.
If you think that's a 50% reduction in TP fed, I think you need to re-evaluate your position.
"holding your WS" until you reach a higher TP value is actually feeding the mob MORE TP, unless you're standing disengaged, waiting for Tactician's roll or regain to give you TP.
edit: I guess you might be referring to Mboze specifically and not TP denial generally, in which case you're still feeding the TP above but you're feeding it to an add and not the boss...so I guess...technically you could be right about the TP feed
That said...the "you'll be at 2k TP plus Warcry" argument has ALWAYS applied for TP bonus weapons. If, for some reason, you're TP bonus'd to hell, then obviously a TP bonus weapon isn't good anymore.