Ok before i begin, i wanna say a few things.
1. Your DK is fine. You know what your doing with him its just that to be damn good with DK you gotta be SPECIAL(imo, there is ONE truly good DK and thats Will).
2. Also, i think you dont have enough exp vs other characters and because of that, DK gets pooped on hard. For example, when you were playing my samus, you stayed away from me. You could have baired my missles, power shielded my zair and then UP+B my entire move set. You also didnt try to spike my tether recovery. Like i said, because you didnt know what to do(not your fault), i pooped on your DK cause hes so damn big and slow.
Knowing this^ i think going Rob is a major improvement. Im gonna give you my opinion on Rob and you take what you want out of it.
1. Recovery. DK has a pretty obvious recovery. Its predictable, stoppable and SPIKE-able. With rob, you can go ANYWHERE. Vertical, Horizontal, under stages as well as hovering above opponents or going THROUGH opponents(kinda like DK).
2. Speed. In the air and on the ground, Rob is faster. His Dash Attack/Dtilt/jab/ftilt/fair(which is the replacement for dk's bair wall)/grab+throw(up/left/right can KO) are all faster than DK but obviously not as powerful.
3. Projectiles. These babies are AWESOME. Lasers are fast(but predictable if the foe watches your head) and do decent damage(anywhere from 5%-16%). Gyro can do 5%-18% but as other uses.
4. Rob is smaller and faster than DK.
The only bad thing about Rob that i think will bother you at first is the fact he cant kill as early as DK. He also cannot back throw INTO the stage to gimp people.
Anyway, what i told you about rob is just the immediate changes you will notice when u compare him to DK. Obviously Rob is MUCH deeper than that and u will learn about that the farther you go into him. Please do not worry about "argh, ive spent 2-3 years on dk and now im starting fresh with rob!" Yea at first you may not do well but its because you picked up a new character. The GOOD thing is, i truly think rob is better than DK AND you already know the basics of reading airdodges/rolls/side steps and spacing. So this already makes you decent right off the bat. Overall, do not leave DK to rob/snake/pika or whatever unless YOU want to. Dont let my words or anyone else sway you into something you didnt want to do in the first place. Anyways, let me know whats up.