I think weaving is simpler to work out from a DPS class perspective. With some exception, rotations are planned out and it's easy to know you're going to do a 3 step combo and can weave in skills easy.

With healing, a lot of what is done is reactionary to what's happening in a given fight. That's something I love about healing. Almost every fight/dungeon for tank/dps is the same...same mobs, same basic progressions. With healing, a missed dodge, skill not being stunned, a buff not going off at the right time, can drastically change the fight and make it unique.

...back to topic (sorry!)...When I know what I'm going to be casting, it's easy to weave. When you're juggling actions on the fly, it's not as intuitive, and that's where players that really know their jobs and skills will be set apart from those just playing the job. I'm working towards that and have tons of respect for those that can already!