TStaff is clearly a better weapon than IFS at all levels....a 30 delay 2 handed weapon has a damage bonus of 17 at level 60. A 40 delay weapon will have a damage bonus of 18.
Post revamp, a 30 delay 2hander will have a 29 damage bonus at 60 and a 40 delay weapon will have a 34 damage bonus at 60 if they go by
http://lucy.allakhazam.com/dmgbonus.html
Damage over time ratios at level 60 (no str mod) for IFS and TStaff:
((2 * DMG) + Bonus) / Delay
pre revamp:
IFS 2.35
Peacebringer 2.433
TSTAFF 2.5
post revamp:
IFS 2.75
Peacebringer 2.833
TSTAFF 2.9
TStaff is always the better weapon versus IFS. Peacebringer is better than IFS at level 60 (sooner than that) too... Once that damage bonus combines with the lower delay, the ratio is better than IFS.
I think fungi is more important than TStaff though, lots of good monk weapons available including IFS