Post by Nulgar
To the above poster...what you said makes no sense and hardly answers his question. DPS Q's are much longer than Tank/Healer, that would waste time not save it.
He meant that by boosting a DPS class/spec, you would not have to wait for dungeons while levelling - the levelling process is actually
a moot point, you can quest or run BGs instead, too, but the OP specifically asked for this.
In general, all classes are "easy" to level no, (in their respective DPS, but also in Tank specs. Levelling in a Healer spec relies on dungeons, but you should have instant queues anyway - when there are enough people around at all, I have seen queues with a Tank, Healer and 2 DPS waiting for a 3rd DPS. Though this should only happen during the off-hours.
So, there is technically not a definite answer as to what is the "most difficult" class to level, barring your personal opinion.
However, skipping the levelling process will
have a negative impact on your experience with the class and most importantly spec, so I'd rather advise against
boosting a Tank or Healer. Though you can ignore this if you plan to read up on those specs and/or use the remaining 5 levels to learn the spec extensively.