I don't think it's wise to earn DEC by delegation when you are already playing the game.

I delegated 750SP and was getting just about 200DEC daily. Making it 1400DEC weekly.

At current rate, I can rent out this SP at 3.25 STEEM weekly on minnowbooster (1 steem per 200SP per week) and I can buy 1500DEC with it (at 0.0025steem on steem engine).

The rates are almost the same. Unless you really have no use of extra SP, it's not wise to delegate for DEC.