I took a look at 2:1 vs 1:1 (ES:FS) using some
Festergut 25-man numbers.
One thing I should note right off the bat is it's pretty obvious that shocks fell off the wayside during this fight (due to priority clashes) as I only had 38 for a 5 minute fight. Given that number, it means my Shocks were only used for an effective 3.8 minutes. This fact actually comes into use later...
Using numbers from Lightning Bolt (on the same fight), I used a 33.3..% crit rate.
Damage Values:
ES = 3248.0 normal ; 7069.3 crit
FS = 1410.7 normal ; 3004.0 crit
FS DoT = 563.0 normal ; ~ 1126 crit (assumed)
1:1
19 FS, 19 ES... 19 * 5 FS ticks = 95 ticks... 32 will crit
6 FS crit, 6 ES crit
6 * (3004.0) + 6 * (7069.3) + 13 * (1410.7) + 13 * (3248.0) + 32 * (1126.0) + 63 * (563.0)
18024 + 42415.8 + 18339.1 + 42224 + 36032 + 35469
192503.9 damage done
2:1
13 FS, 25 ES... 13 * 6 FS ticks = 78 ticks... 26 will crit
4 FS crit, 8 ES crit
4 * (3004.0) + 8 * (7069.3) + 9 * (1410.7) + 17 * (3248.0) + 26 * (1126.0) + 52 * (563.0)
12016 + 56554.4 + 12696.3 + 55216 + 29276 + 29276
195034.7 damage done
Result
2:1 greater by 2530.8 damage or 1.3%
To be able to calculate some variance into this, I wrote a small excel spreadsheet to do all the math for me (and allow me to change values easier). The spread obviously shrinks as you gain more shocks and also as you gain more crit chance.
But do recall that I mentioned that shocks were only used an effective 3.8 minutes with the data I used. This means that there's a good chance that in this same scenario that I wouldn't have overwritten Flame Shock using a 1:1 ES:FS ratio. Since I used a simple Flame Shocks * 5 to get the amount of DoT ticks for the 1:1 calculations, that means I probably would actually get 6 ticks for a few of those.
Also, Rouncer, I did some quick math on the FS Glyph and I'm seeing about half the potency of the Lightning Shield glyph, but do consider that's with 2-piece T9. I used Saurfang to try to ensure there was less chance of having a Lightning Shield proc from extra damage (i.e. Pungent Blight on Festergut). The LS glyph provided 16169.33 more damage and the FS glyph would provide ~7604.58 more damage. Given the fight's duration, that would be 56.73 DPS vs 26.68 DPS.