We do care about and actively balance at lower levels. Our goal is to make the game as fun and balanced at possible at all levels, however, greater scrutiny from a design standpoint, as well as by the whole community, is placed on the end game. From a perspective of a systems designer, the end game as of patch 4.0.1 is now level 85.
That said, we will be making several balancing changes in patch 4.0.3a based on what we've been seeing since patch 4.0.1. With regard to lower level players, we plan to adjust damage and healing for all classes from levels 1-79. The base points of almost all spells and abilities are being reduced in order to bring combat times at low levels to a more acceptable length. Some specific spells/abilities are being reduced in damage even more, and in the case of most abilities that deal weapon damage, we're going to make the damage percent scale with level. So as an example, Sinister Strike is currently planned to do 42% weapon damage at level 1, with the percentage of weapon damage rising per level up to its maximum potential at 80.