What is this? No seriously, what is this? Your burst damage multiplier only cares how many steps there are in the skill chain, not what level it is. You do know that there is a difference, right?
Are you confused? I said nothing about multistep skill chains, only that you should stick to level 1s. Stone > Aero > Stone is a 3-step Scission and it is still only a level 1 skill chain!
Let me introduce you to our level 2 skill chains:
Liquefaction + Impaction = Fusion, closes with Lightning and the element is Fire/Light. Missing out on weather and staff bonus for either the closing spell or the skill chain.
Induration + Reverberation = Fragmentation, closes with Water and the element is Thunder/Wind. Again, missing out on weather and staff bonus. Even worse, you're limited to using Windstorm because Thunderstorm will hurt your closing spell's damage (not a problem at 90, since our highest spell is Aero V, but it is likely that Thunder V is still in the cards for 99).
Detonation + Compression = Gravitation, closes with Dark with a Dark/Earth element. Finally, a chain that lets us close with the same element as the chain itself! Unfortunately, it requires Impact or Noctohelix. Impact is fine I guess. I don't have it so I don't know how it compares in damage to our other spells, but helix spells are terrible to close skill chains with due to their low initial damage.
Transfixion + Scission = Distortion, closes with Earth with a Water/Ice element. This can only be opened with Luminohelix, and again you give up staff and weather bonus for either the closing spell or the chain itself.
All of the other level 2 skill chain possibilities require the closing ability to have 2 elements, which SCH cannot do using Immanence.
The only way we are doing level 3 skill chains is by closing with a WS:
http://www.youtube.com/watch?v=bEcEi7zOaBU (not my video)
You're giving up your first 2 spell's damage so you can get TP for your WS (or you're stuck relying on wings/Shikikoyo). Brilliant! The damage on the video isn't very impressive despite being up against EP, but she doesn't appear to be maximizing her WS damage either (no weather, no gear swaps, etc.).
Of course level 2 and level 3 skill chains get all the bonuses that level 1's get, but you are crippling your damage output by going after them due to the limitations SCH has to live with. If you do a nice neat 2-step Detonation with Thunder IV and Aero IV, you can follow it up with a bursted Ebullience Aero V or Amenohelix. Your closing spell, skill chain, and bursted spell are all the same element (allowing you to easily take advantage of staff/day/weather bonuses). This maximizes your damage more than a 3-step anything else using the same number of Strategems.