Further more,the block animation has a similar problem in my opinion.
efbr=fbr*120/(fbr+120),no cap.
speed_mod=(50+efbr)*256/100

block_speed={256*Base/[256*(50+efbr)/100]}-1

Base=3(ama/ass/pal),4(barb),5(sor),6(nec/dru)

and the table looks like:
Ama/Ass/Pal(Base=3)
=================
fbr--efbr--speed(frame)
0-----0------5
13----11----4
32----25----3
86----50----2
600---100--1
=================

Barb(Base=4)
=================
fbr--efbr--speed(frame)
0-----0------7
9-----8------6
20----17----5
42----31----4
86----50----3
280---84---2
=================

Base=5(sor) and 6(nec/dru) are same as fhr-tables.
dis one:

Sorceress(Base=8)
===============================
fhr-----efhr-----speed(frame=1/25 second)
0---------0--------15
5---------4--------14
9---------8--------13
14-------12--------12
20-------17--------11
30-------24--------10
42-------31---------9
60-------40---------8
86-------50---------7
142------65---------6
280------84---------5
1480----111--------4
==============================

Druid/Necromancer(Base=7)
=======================
Fhr--efhr--speed(frame)
0-----0-----13
5-----4-----12
10----9-----11
16----14----10
26----21-----9
39----29-----8
56----38-----7
86----50-----6
152---67-----5
377---91-----4
=======================



confirmed by ruvanal, hammerman, ...