I live in Olimar country, I personally think it's 55:45 Oli's.
Olimar juggling DK is
not as big of a deal as DK juggling Olimar. We have the very simple option of going to the ledge, Olimar isn't going to threaten us offstage except with a up-b maybe, but that's so telegraphed. When we get hit up, we'll probably take 40% from your stupid u-air. Our range and speed let us poke at Olimar while he's landing without having to worry about the n-air, while Olimar's weight and fallspeed makes it take forever to get down and any hit puts him right back up. Even if you momentarily land vs DK, you now have DK close to you while you don't have anything set-up and he has the option to use down-b, go for grab, d-tilt, jab, whatever.
About approaching,
(credit goes to Ook!)
This is a necessary pre-req to start approaching, lol. We have the tools to approach Olimar very well, with up-b, down-b, f/d-tilt. It's still hard and we'll fail more than not. Without having to worry about purple toss, it's a lot easier to just throw out down-b's or up-bs timing the super armor closer to impact. Oh, I should mention that DK should
never ever try to approach from the air. Our grounded options can challenge him somewhat safely, b-air will just get you shieldgrabbed easily.
For killing, Olimar has a much easier time lol. Olimar will get kills when we try to approach him with up-b/run up and shield/are in the air for some reason and we fail. Down-b is a relatively safe way to avoid kills, although red f-air can catch you with bad DI. Remember that DK
doesn't have to hold down when he holds his down-b, so hold up after you start it. DK will get kills by hitting Olimar out of grab armor with d/f-smash or punch, reading a bad landing, or gimping. DK's actually pretty good at gimping if the Olimar doesn't get hit really high initially. Up-b is extremely powerful at keeping him offstage and eating his double jump.
Our counterpicks are ugly vs. Olimar. If I was an Olimar in this match-up, I would first and foremost ban Brinstar. The acid gives us oppurtunitys to juggle/chase you without having to go through the pain of apporaching, the curves make your grabs awkward, and the blastzones will spell death at something stupid like 60. And it's too small for you all to run away and go for pivot grabs all the time. We have a lot of tricks there too.
Other than Brinstar, Yoshi's and Pokemon Stadium 2 are very strong stages for us. Yoshi's for the usual reasons. PS2 is just hilarious vs. Olimar. DK is only like pretty good on it, we don't mind any of the transformations, but Olimar is just hilariously bad on all but the ground/normal transformation. And we're still better on the ground phase than you all are.
As DK, I'll be banning FD/Halberd. Probably FD, I personally can't stand not having platforms, and at the very least, Halberd gives us interesting ledge options, earlier d-smash kills, and some slanted slopes to work with.
We have the potential to ruin Olimar very quickly, it's just that we don't get very many opportunities to do this. Olimar, on the other hand, wins on neutral ground and has many opportunities to just tack on damage.
I honestly know nothing about DK planking Olimar. I have an Oli friend who says he tested it and that it's impossible for Olimar to beat DK's planking on Yoshi's specifically, but it'll get beat elsewhere.
For convenience, here's a post Will made regarding the match-up. This was back in 2010 so he's probably learned some new things about the match-up, but I'll leave that for him to answer.
I have a lot of experience with this matchup. So I will give you all the suggestions I can think of =)
First off, I think up b is a pretty good way to kill the pikmin that attach to DK. However, there are times when it is more beneficial for you to jump and up air to get them off of you, since up air covers most of DK's body (at least his torso and head areas) and gets you out of the way of more incoming pikmin that are being tossed. Anything that up air doesn't kill, b-air/n-air will. Up air is usually the best option imo since it's really fast and covers most options. In addition I think up tilt is another good grounded method of killing pikmin, or down smash if you are far away from him.
Also, I saw you tried to go for that up b gimp from the edge but missed the timing =P That works reallllly well against olimar if you hit him out of his double jump with it. Then you drift back onto the stage or regrab the edge depending on when you think he is going to up b. But that is a great tool toward gimping him as well.
Don't be afraid to go mad far off stage against Olimar and throw out a b-air, bc even if you miss he will be forced to recover low, in which case your up b can beat him back to the edge before he can grab it with his up b. Also, it's fairly easy to expect an air dodge or down b super armor, so just waiting for it then b-airing usually works well.
In terms of purple pikmin.... sigh. Those things really are a pain in the ***. In order to prevent most of them from coming out, you're going to have to stay on him. And its really hard to pressure him when the only true ways in are grounded up b and down b.
In terms of getting through and killing the purples, you absolutely need to use fully charged punches as often as possible. In addition to killing the purples, it beats Olimar's grabs. Yes, Olimar cannot grab armor the punch, if he grabs you while it hits him, the grab auto breaks!
Also, in general a good approach if you can get in close to Olimar- down tilts on his shield. It's hard to get in that close, but if you can, spam those d tilts!! Olimar's grab out of shield is too slow to prevent the tilts from hitting his shield/eventually poking through.
Keep asking and I'll keep putting forth what I know. =)