Это сработало для меня. Не применяйте rotateLabels (-45), как я применил в вопросе. установите ShowLabels = true и labelSunbeamLayout = true, как показано ниже в файле nv.d3.js.
//============================================================
// Public Variables with Default Settings
//------------------------------------------------------------
var margin = {top: 0, right: 0, bottom: 0, left: 0}
, width = 500
, height = 500
, getX = function(d) { return d.x }
, getY = function(d) { return d.y }
, id = Math.floor(Math.random() * 10000) //Create semi-unique ID in case user doesn't select one
, container = null
, color = nv.utils.defaultColor()
, valueFormat = d3.format(',.2f')
, showLabels = true
, labelsOutside = true
, labelType = "key"
, labelThreshold = .02 //if slice percentage is under this, don't show label
, donut = false
, title = false
, growOnHover = true
, titleOffset = 0
, labelSunbeamLayout = true
, startAngle = false
, padAngle = false
, endAngle = false
, cornerRadius = 0
, donutRatio = 0.5
, arcsRadius = []
, dispatch = d3.dispatch('chartClick', 'elementClick', 'elementDblClick', 'elementMouseover', 'elementMouseout', 'elementMousemove', 'renderEnd')
;