giving all monsters the same SP is a bad idea, because not all monsters are created equal. some things are just harder than others.
More overall content is needed, dungeons are good because it can allow you to level while also doing content.
The old SP system with less randomness party share exp option and some tweaks prolly would have worked best for making all monsters viable exp, or at least with the right setup, any mob is sweet. But it is gone and not coming back.

there are other ways to get decent exp, but maybe the answer is not to base the content so heavily around exp. Have other ways to improve your charachter, that are entertaining. More variety.

Anyhow to fix the sp, they need to come up with really good values to determin each monsters difficulty, I agree that the 10 level limit encourages you to smash crappy mobs really fast. However it is possible after they change battle we will be so weak that 10 levels will be hard. but that will prolly just slow exp, and make small parties suck.