k2tog tbl twists the stitches although it will still be left-leaning. It depends on the individual knitter, a bit like tension. You might like to try out some different decreases on a swatch and see which looks best the way you do it. Slipping the 1st st. kwise and the 2nd one pwise gives a flatter result for many people (check out Nona's post on trying out many deifferent decreases). And try to slip the st.s gently without stretching them.
keeping the decreases away from the needle bridge points (where the stitches go from knitted on needle 1 to needle 2 etc.) may help too. Also they will even out with time and blocking, or you can tighten them up and redistribute the slack.