There is for nukers(mages/casters) a way to train the nukes faster. If you have under 10% of your hp(when it blinks) you get double xp for them. It also stacks with manuals.
If you are going for white clans they in Song Shan (shaolin starting area) is a spot with a lvl 63 tiger. The tiger is unable to get under the due to a in-game bug. You can nuke him very well Laughing .
At the black clans it is a bit harder. There is also a spot were mobs cant pass but its at the twin brutes spawn so it will be imposible to lvl the nukes there is you outlvled them.
The next place that is buged is in CC2. You should probably be in a hero band/league by now (SM) were you can train nukes but by then you probably maxed them out. Smile