K3K can be really easy.
For traprat, make sure you can summon 3 Elvensong. Those will help you tank while you take out totem with thorn wall.
A lot people have already discussed items, so I wont go into that.
Know the lay out of K3K is another Key factor. You need to know which totem covers which area.
So heres a quick example of K3K farming pattern. You spawn at the Blue, move up, distract the crowd with elvensong, this will clear a big area you can retreat to. You should also move just enough that totem show up at the tip of your screen.
Step 2, clear the totem to the left and top, draw the skeleton if you need to, the totem before the necro can be tricky, but you can create a neat pocket for yourself with elvensong.
Then rinse, repeat for 2nd necro, there's a couple spot where you can barely hit totem with your thornwall from the edge of the screen, find those in the lower difficult before you start running this.
Go around and clear the last couple totems, make sure you engage away from the direction of the necro.
I would totally recommend running some Terror K3k. It's the easiest place to find set and level 100 runes.