I didn't intend to say that you shouldn't have any other skills. Obviously, you can't just have flask of fire and throwing blades, since you would have to cool down eventually against high HP targets.
At mid range, however, tempest doesn't have anything that matches the dps of flask of fire + throwing blades. If I recall correctly, on the same character, when long shot (with damage upgrade) pulled 8k max damage using the max-range 1700% damage bonus, throwing blades could reach 10-12k damage per hit at the end of the sequence due to consecutive stacking of sunder/damage bonus, with the duration passive to flask of fire. Since throwing blades is 4 hits, that is 40k damage in one skill use in the same amount time it takes to do about 2-4k damage from long shot at mid-range.
At long range, I also like the unquenching upgrade, since you can string 4 shots of long shot (6 if you have passive duration boost).
When flask of fire isn't up, I use flask of frost and flask of lightning, during which the other skills are fillers until flask of fire is up again. During flask of frost, shadow strike is pretty good against chilled opponents. During flask of lightning (with lightning damage upgrade), explosive shot is pretty good to register hits on a large number of enemies. When I played tempest, I used the 3 flasks, throwing blades, shadow strike, long shot, explosive shot, and leaping shot (didn't use focus due to one of the trial options).