I believe the d-scan immunity on Recons is good because it further breaks a method of intel gathering and thus allows investigation of the effect unreliable intel gathering has on the game and play styles. This information can then be used in a future development of new or altered intel gathering mechanics.

tl;dr You have to cut the body open for an autopsy.

The definition of Reconnaissance is military observation of a region to locate an enemy or ascertain strategic features.

This is normally done by hidden and undiscovered units. A recon ship should excel at that, or it wouldn't be specialized for recon.

This is good as it allows intel gathering from all sides, which could then lead to more moves made against one another. Conflict and desire for increased power are the driving factors of EVE. Alliances moving against one another create some of the best content in EVE. Gathering intel on one another will generate conflict, either from an alliance finding a vulnerable target or from the recon being discovered.

IMO this can only be a good thing. If someone AFK cloaks in your system, and you all dock up until he leaves, you are missing out on some fun times. This is when you should be planning to counter whatever action the recon ship is there for. The ability to influence actions from other players it what the D-Scan immunity is going to enable. When you see someone enter local and can't scan the ship, docking miners and undocking PVP ships should be your action.

It strengthens an entire playstyle: The fleet prober