Dubbed "Sky-Fall", this ability would essentially be a way for (specifically Alliance) Paladins to drop quickly, strategically, (and very brutally) onto a battlefield or to (if used tactically) assassinate a target of interest via a seemingly lethal vertical free-fall, while averting death upon activating Divine Shield.
Because I'm not too great at explaining things, I have hastily provided a sketch of the various steps included to perform a successful "Sky-Fall" maneuver, in order to provide visual aid.
Step 1: Signal Mount (via flare gun)
Step 2: Express Mounting. Grabbing onto an armoured limb of the mount within seconds of it's entry.
Step 3: Vertical Take-off. The objective of this step is to go as high as one's mount will/can go. This also brings up the bond between master and mount. For instance, the stronger the bond, the higher up the mount will go before leaving the master. If the bond is weak, the mount will disband before reaching the optimal altitude for Sky-Fall deployment.
Once the mount has left, the master/Paladin performing the ability will have only milliseconds to position themselves within mid-air for the free-fall drop. Said positioning can be simple or complex, depending on how they with to drop. Upon positioning oneself, momentum will be gained and the unit will be dropping at climbing speeds.
Ex. The diagram shows a complex maneuver to position oneself, reserved only for veteran "Sky-Fallers".
Step 4: Application of Divine Shield. Said spell should only be used seconds before impact with either the ground or the target, as using it before (ie immediately after mount departure in step 3) can be fatal and the Paladin can die upon impact.
Step 5: Impact imminent.
Step 6: Impact. The force from the Paladin's momentum and the invincibility yielded by Divine Shield will utterly crush the opponent, with the Paladin unscathed, leaving a seething holy crater in his wake as he engages the Horde in glorious combat.
This also raises another question, the effectiveness of Divine Shield both IC and in existing lore. I recently had a discussion with a friend regarding the limits that Divine Shield possesses. He pointed to the novel Arthas explaining that Divine Shield only deflects piercing effects, and that the user could still feel pressure, pain, etc.
Another question, is Divine Shield, in Lore, a bubble, or a full protective magical layer that encases the user (similar to the Halo Series' spartan/elite shielding)?
Here's another image to assist in visual aid, containing a particular Alliance-affiliated Sin'dorei:
Discuss Moon Guard.
The idea itself, the limits of Divine Shield, Azerothian physics, etc.