It seems you're right, Deadly Cannon is not working how it should. At last in the log I checked my maximum Full Auto crit was about 175 % of my maximum non crit. With a 75% crit multiplier there are missing 30% DMG. Will do some testing today if Deadly Cannon works or not.
As I said, I did a bit of testing:
I had 4 test setups:
1. Deadly Cannon not skilled, Curtain of Fire procs NOT used (Control Sample)
2. Deadly Cannon not Skilled, Curtain of Fire procs used
3. Deadly Cannon skilled, Curtain of Fire procs NOT used
4. Deadly Cannon skilled, CUrtain of Fire procs used.
(critical Multiplier was 76.28 %)
with these setups i could test both, Curtain of Fire and Deadly Cannon, working or not.
1)
Spell Count Avrg. Dmg Min. Damage Max. Damage Min. Crit. Max. Crit.
Grav Round 24 1568.08 1234 1332 2130 2361
Full Auto 23 1190.43 896 1071 1713 1902
Demolition R. 7 2815.86 1970 2032 3349 3546
2)
Spell Avrg. Dmg Min. Damage Max. Damage Min. Crit. Max. Crit.
Grav Round 1734.73 1219 1345 2172 2349
Full Auto 1616.26 1054 1280 1930 2265
Demolition R. 2210.33 1930 2010 3416 3416
3)
Spell Avrg. Dmg Min. Damage Max. Damage Min. Crit. Max. Crit.
Grav Round 1666.93 1242 1345 2165 2360
Demolition R. 3065.82 1826 1999 3929 4181
Full Auto 1116.37 890 1064 1635 1862
4)
Spell Avrg. Dmg Min. Damage Max. Damage Min. Crit. Max. Crit.
Full Auto 1466.33 1053 1287 1864 2256
Grav Round 1707.26 1236 1340 2200 2364
Demolition R. 3290.38 1931 1983 3960 4177
If we take the first two samples and compare the Full Auto dmg:
min dmg
896 * 1.25 = 1120 | 2) == 1054 ~ (117 %)
max dmg
1064 * 1.25 = 1330 | 2) == 1280 ~ (120%)
Curtain of Fire is working, it is not the 25%, but this is probably because of my small sample Size.
Taking the the third of fourth sample, we see the crit Damage of Demolition Round is higher than in ther first and second Sample:
3) max dmg (Demolition Round) max crit (% of estimated value)
1999 *2,0628 = 4123, ... | == 4177 (~101,3 %)
=> Deadly Cannon is working for Demo Round
3) max dmg (FullAuto) max crit
1064 * 2,0628 = 2194, ... | == 1862 (~84,9 %)
1064 * 1,7628 = 1875, ... | == 1862 (~ 99,3 %)
=> As we can see Deadly Cannon provides no 30% Critical Damage Bonus for Full Auto as stated in the Tooltip.
Full Auto is using the standard crittical multiplier.