Should I power up my lvl13 48.9℅ IV dragonnite with DP/DC

I think the damage output for your 49% DB/DC Dragonite will be pretty similar to DB/HB or DB/DP Dragonites with slightly better IVs. With 0 def IV, it might take a bit more damage in return, but that's probably mitigated by the ease of dodging when using DC.

I would suggest testing the DB/DC Dragonite as is, against lower CP defenders to see if it gives you the feeling you're looking for. I'd imagine the biggest difference to a DP or HB Dragonite would be its ease of use. Personally I have little to no problems with the clunkiness of HB, so I probably wouldn't bother personally. Especially since it has neither good IVs or high level already.

wait

With same IV at lvl 30 DB/DP is around 94% of DP/DC, according to qMike's sheet. 0,0,0 Dragonite is about 77% of 15,15,15 Dragonite. So we can guesstimate that the difference IV's make (~51% vs 89%) is something like 9-10%. So, no. Though DC is quite nice to use as it executes so fast.

Kinda in the same boat, I caught a 1/1/14 2400 cp DB/Dc the other day and am debating powering it up as well. The main problem for me is, as it prolly is for you, where I will get the candy to power up my 3 3k Dragonites? If I keep evolving I wont be able to power the ones I have up.

Heres a video of 3 different DB dragonites at same level fighting same lax.
https://www.youtube.com/watch?v=4TJzq7qTHGQ