Its funny for me to say this but Dynasty Warriors 8 + Xtreme Legends (or for those with their PS4s and on PC, DW8: XL Complete Edition) i feel like is one of those DW games that i feel that they got it right when it comes to making your moneys worth.
I remember back in the older DW titles that most of the musou mode/campaigns of each faction or individual character only lasted for a few hours or even less depending on what difficulty setting you were playing on. Most of the length in a typical DW campaign was padded with you either being undergeared or underleveled when getting into the later battles, thus there is a need to grind by playing Free Mode. However, in DW8, while there can still be the case of being underleveled or undergeared in going to the next few stages, the game does help the player by auto-leveling characters who are needed to play on said particular stage, thus you won't be tackling a battle at level 1 but instead you have that needed character scaled already at the minimum level for that particular stage. And to cut things short from how DW8 works and more into its musou mode, each faction has DOZENS of stages in their respective campaigns, and counting XL with Lu Bu's own musou mode, you have 4 Factions to play with, and each faction's story mode has dozens of levels with such grand scale as well, and it can basically take anyone playing at an average pace hours and hours to just even get to half of each faction's musou mode. It also helps that you can even replay Musou mode levels in DW8's story mode so that in case you missed an important event, you can do so and open up an alternative story mode path for said faction, thus adding even more things to do. And that's just the Musou/Story mode.
There's also Ambition mode which is basically some content outside story mode, and its really fun, but most of the battles in Ambition mode are short scale skirmishes, very much the opposite of the bodycount fiestas that you can easily do in most of DW8's levels. The best part is that whatever that is unlocked or acquired in Ambition mode will also carry over to Musou and Free mode, such as weapons, bodyguards, forged weapons, and whatnot.
TLDR, Dynasty Warriors 8 + Xtreme Legends (or those who really were efficient, DW8XL: Complete edition on PC and PS4) is worth all the pennies and dimes, especially if one has been playing the whole DW or warriors series in almost in its entirety.