Welcome to Librarium Online!
Deff Kopta x4
Killa Kan x3
Killa Kan x3
I'll be playing against Nids(mainly Guants) and CSM (mainly thousand sons)
I'm going to comment on both your armies here, since they are pretty similar. I play vs nids a lot, so I'll concentrate on them.
First off, burna boyz on the ground are nid fodder. You most likely will not be able to use the flame template even once. Nid's have insane mobility on the ground and can easily outmaneuver a unit of burna boyz to wipe them out without getting templates of death. Instead of the burna boyz, I'd put their points into....
More boyz. I'd run the max squad size vs nids. I'd also considering making one boyz squad shoota boyz, and giving them big shoota's. The only time I've come out ahead vs nids in CC, is when I have an utterly excessive amount of boyz in a squad.
Loota's are a god send vs nids, but watch out for gene stealers. Sometime it's worth having a kommando unit, just to be able to place them to intercept the gene stealers.
If you need more points for anything, drop a DCCW off the dreads, and ptu a scorcha in its place. Easy 10 points right there.
Nid's hate kan's and dreads. I usually run 9 killa kan's vs my buddies nids, with 6 rokkit kan's, and 3 grot kans. I find that many nids (especially warriors) have an excessive amount of wounds (3 on the warriors), but will generally have T4. Thus the grotzooka becomes worthless vs them, but the rokkit's instantly kill them with no save. The zooka's are still awesome on mobs of gaunts though .
If you find that boom gun is ineffective, just replace it with another group of 3 kans!
Last but not least. Consider separating your deffkopta's. Put 1 in each fast slot (maybe drop the extra one). This way you can use them as independent units, to harass and annoy. (3 different direction scout moves can be devastating on turn 1). This also prevents them from ever having to make a leadership roll.
Agree you need more boyz, burnas are not going to live long, and the deffkoptas. For points you will want to drop the heavy armor on the hard boys, it really is not worth the 4pts considering an ork costs 2 more. Also but a burna on the mek instead of the PK. It stats in the FAQ that the attack squig give you an extra attack at base strength, so 4 or 5 on the assualt. Pluss the burna will be better vs. nids.
Repainting Orks not sure how many points yet
Warriors of Chaos shelved until further notice