Using simple math and delved dmg for comparisons, I did some "opening fight" vs "dmg over time" comparisons between a sorc and a warlock. I thought some numbers could be helpful to quell some of the wild exaggerations being flung around. I chose the 2 most common FotM specs for each class and use delved dmg as each class can equally increase dmg (buffs, gear, etc.) to the common 3x delved dmg ranges. I compared the first 6, 12, and 24 seconds of combat time to compare front-loaded dmg vs dmg-over-time, factoring in a warlock's opening DoT for max dmg.
Avg dmg per second calculations:
Warlock (1st 6 seconds) = 1265 (3 chambers + 1st 4s DoT tick = 239+109, 179+225, 179+225+109) / 6s = 211/sec
Warlock (beyond 6 seconds) = (225 + 109 / 4) / 4s = 84/sec
Sorc = 179 / 1.2s = 149/sec
Dmg rate (1st 6 seconds of a fight): Warlock = 211/sec, Sorc = 149.
Dmg rate beyond 6 seconds: warlock = 84 (counting DoT ticks), Sorc = 149/sec
Total dmg at 'n' seconds (Warlock vs Sorc):
6s : 1265 vs 895
12s: 1769 vs 1790
18s: 2273 vs 2682
As expected, warlocks have a lot more front-loaded damage, but they're far inferior in sustained damage output over time. I liken a warlock to a shotgun and a sorc to a machine gun. Personally, I'd choose a shotgun for 1-on-1 fights and a machine gun on a battle field.
Notes:
1. Warlock is spec'd 43H-30W-12C (FotM), sorc is spec'd 36M-40B (FotM).
2. Cast times are based on hard-coded 2s for chambers, 4s for primary+secondary, and the common 1.2s for the sorc's LTs.
3. Warlock starts with 3 chambered casts, has to switch to regular casting afterwards, likely using noninterrupt primary + LT, possibly using no-power primary intead of noninterrupt if they're not under-fire.
4. Warlock's 3 chambers are: bolt+DoT (239 + 109/tick) and 2x DD+LT (2x 179+225).
5. The warlock can substitute the 1st chamber with DD+LT for +7 dmg on the first cast, but there'd be a huge dmg-over-time loss w/o the DoT's 109d ticking every 4s.
6. Sorc's LT (179 delved) is base, not spec, std for "big nuke" usage. Warlock's bolt and DD are base, LT is spec (only possible choices). Sorc can use spec DD instead of base LT for less less power usage, more dmg if spec'd 45B, and 2.8s delved cast times vs base LT's 2.5s cast time.
7. I don't know if it's possible*, but if you can chamber 3 bolts instead of 1 bolt and 2 DDs, the warlock's total dmg output increases by 120 for the initial 6 seconds.
* My warlock doesn't have 30 WC yet.