Tourist is hard to start out with, then gets relatively easy. High-level tourists (post-Quest) used to be extremely easy due to the Platinum Yendorian Express Card and a wand of polymorph being able to provide unlimited polypiling (Dr. Efembe, I presume!). Now restrictions on recharging wands and on polypiling take away that advantage.
Archaeologists are also hard to start out, but Lawful alignment, good aptitude for the sabre skill, and a starting tinning kit make them easier later on.
But that might be because I focussed on the supposedly harder classes after doing Valkyrie and Wizard.