And here are the 25 least consistent:  

#	Artist	Spread	Average
1	Sepultura	25.022	67.55
2	In Flames	21.621	60.74
3	Megadeth	19.333	71.54
4	Krieg	18.455	71.19
5	Deicide	18.007	74.15
6	Deathspell Omega	17.925	83.93
7	Metallica	17.863	69.16
8	Virgin Steele	17.747	74.5
9	Six Feet Under (US)	17.601	55.15
10	Dissection (Swe)	17.275	70.67
11	Sentenced	16.626	66.79
12	Moonspell	16.312	78.28
13	Nuclear Assault	16.234	72.04
14	Mayhem (Nor)	15.754	67.69
15	Machine Head (US)	15.453	55.06
16	Within Temptation	15.379	61.25
17	Slayer (US)	14.537	73.97
18	Children of Bodom	13.943	77.63
19	Black Label Society	13.937	75.05
20	Pantera	13.921	69.97
21	Celtic Frost	13.717	73.4
22	Cannibal Corpse	13.476	74.89
23	Motörhead	13.319	78.23
24	Danzig	13.037	80.0
25	Pain of Salvation	12.934	87.77

 

Most of these follow the "great once, crap now" pattern (I think we can now officially call this "Sepulturding"), which makes one wonder whether developing a fan-base is really worth the bother in the end. Deathspell Omega deserve a special note: if they'd had the sense to release Infernal Battles under a different name, their other 4 albums would give them a standard deviation of 1.66 on an average of 92.86, and we could have a very obscure statistical argument over whether that means they are in fact even greater than Fates Warning.