Normal mode is pretty challenging if your group can only invest 3-6 hours a week. This is not bad at all. Some encounters are hard and need training to get into the routine.
ToT will be PUGable if enough casual players have the experience that is needed or if enough overgeared/experienced people are in the group that trivialize the encounter.
If you want the easy mode. Just do LFR. That is what LFR is for.