What is the soft haste cap for a raiding elemental shaman that allows for an extra lightning bolt cast in between lava burst casts? Also, what is the raiding hit cap for draenei elemental shaman, without boomkin or spriest hit buffs?
You have 2 questions -- atm, I'm answering the second part of your question (about the +hit): you roughly need around 342 hit rating.
WoWWiki have a very good explanation about +hit. Scroll down to the end of the page and it'll give you a complete list of what hit rating required given the buffs and/or talents you have.
In regards to the haste:
Each 820 Haste allows you to fit another Lightning bolt in between your lava burst (the first one is minus 5% for your totem and so is only 656)
*Ele shamans have 5% haste just from totems
In regards to hit it would be 13% or 342 with no raid buffs (other than Heroic presence and elemental Precision.
522 haste rating is the haste softcap for an elemental shaman properly buffed*
*Wrath of Air totem, proper talents, etc.
For an Elemental Shaman, there is no "soft haste cap" and only ideal haste levels where extra Lightning Bolt casts will be able to be squeezed into our rotation before the next Lava Burst becomes available. Haste is their #1 scaling stat with Spell Power and Crit after being Hit capped.
This would also include having all the appropriate Haste buffs within a raid: Wrath of Air Totem (5% spell haste) and Swift Retribution Aura/Improved Moonkin Aura (3% haste).
To the second question, hit cap levels for elemental shamans depend on what faction they are (Alliance or Horde).
Add in what you need (hit debuffs, hit talents and aura when applicable):