The new DLC comes out and all of a sudden shit is different/harder. Why would people play the new stuff over and over again when they can just go back to VoG or Dailies to breeze through their daily/weekly servings of <whatever-the-fuck-currency>?

With the radiant nonsense, there's more incentive for the masses to play the new Raid and level up your standing with Eris (funneling).

Assuming you did Eris' bounties every day except those 2-3 when PSN was down, you should be rank 4 today even if you main a Titan. If you run a Warlock or Hunter, or used the bounty duplication glitch/exploit (shame on you) you probably hit that point days or even weeks ago.

So now you can just convert all those Energy into Shards.

Admittedly it took a month, but unless you've been very lucky you probably cant get more than 2 characters to 32 yet anyway, and you still wont have enough shards/energy combined to level all 3, so you've plenty of time to rank up Eris if you missed a few days.

Only one, and Bungie recently sort of voided it.

You're right that they seem redundant with the only difference being RNG. Other materials and currency are acquired in different way, encouraging a player to do different things to get what they want. Shards and Energy are acquired in all the same ways.

The only place that isn't true, and my only thought, is when you break down either weapons or armor. This forces a sort of trade, where you may have to break down a weapon in order to gain power with a second weapon.

However, it seems that even Bungie thought that system was a little nuts, as the new exotic shards work for both weapons and armor.

I fully expect Bungie to continue to tweak the currency system as time goes on, not just by adding new currencies, but by combining them and giving us exchange methods.