[550] Lava Lash plus [350-400] instant main hand and off-hand white damage along with close to [100] damage from double Flametongue weapon procs equals roughly 1k damage. And I'm not sure why you'd say Primal Strike is garbage especially seeing there is a 45% damage increase talent.
In response to your final statement, a good player can do very well in games, regardless if the spec is 'viable' or not. I have even seen resto shamans (Dasfizzla and Sloppyheals) do very well even though it's considered one of the worst and least played specs in the bracket atm. Keep your generalizations to yourself.
1. The discussion isn't whether or not someone can do good with a particular class/spec. The discussion is about enhancement shamans @ level 19, to which I responded that right now they aren't very viable at all compared to any other dps spec. I listed the reasons, and then concluded with the fact that they will be getting a pretty good buff in MoP.
2. You said 1k dmg in a single global. Lava Lash is a 10 sec CD, it goes by your offhand damage, which is halved because it's your offhand. Primal Strike is an 8 sec CD and it's just normal weapon dmg with no modifiers EXCEPT for the 3 pt talent, which despite being absolutely necessary is still garbage. There's a global CD inbetween both Primal Strike and Lava Lash, and then 8-10 seconds of down time before you can use either one again.
Now, by comparison, a level 29 shaman's absolute best DPS ability is Stormstrike. It's head and shoulders above Lava Lash AND Primal Strike put together. and if it were available at level 19, enhancement shamans would be on par with every other dps, like they are at 29.
Stormstrike is 326% dmg with BOTH weapons, Lava Lash is 300% (with flametongue on the OH), and primal strike is normal weapon damage from the MH. When you compare Primal Strike with the ability that replaces it @ 29, yes, it is absolute garbage.
3. You're talking about the stars aligning and getting crits on EVERYTHING. Can you do a decent amount of damage on a shaman? Sure. Is it a competitive amount of dmg? Nope. And the reason is the lack of combat up time. It's way to easy to kite a shaman around and kill him before he does anything useful. If your goal is to rock a 19 shaman right now, it should be to spam Purge cuz that's all that's really useful, except for the off change on the stars alignment.