I wondered if others thought the game would be too easy with:
1. Multiclassing alone
2. Feats alone
3. Rolled stats alone
4. A combination of any two of these
Let me add one category, which I find even more "fearful":
5. High level games with an all full-caster group.
When you have a 14th level group with a diviner, an illusionist a necromancer and a land druid, it can be quite challenging to challenge them, and tailor-made encounters might be the DM's last resort.