I played the story-RPG-chapters before, and I have to say, they are much better.
To make an arena spin-off is a nice idea, but your tactic-engine isn't good enough that this will work in such a stand-alone. Indeed, I finished your spin-off (on every 3 difficulties), bit I am still not convinced. The mathematical aspect behind your engine isn't well balanced.
1. New characters with new tactical abilities (maybe new chars for your 3rd chapter?)
2. in difficulty "brutal" you decided that mutliple-field attacks of the Hero will affect allies as well. I liked the fact, should have been introduced way earlier (and also for the multiple-field healings, please)
1. Hero has a too tactical focus (I know it is the main char, but in an arena team-fight game the others chars have to be important too. With the Vengeance-attack the hero can kill everyone in a safe corner if the enemy is inly coming from max. 2 sides)
2. only Hero has multiple-field attacks
3. mutliple field attacks are too powerful. Lowering the damage in comparison to single-field attacks would rise the strategic usage
4. Difficulty "normal" was average, "hard" was very ez, only "brutal" were challenging at the end in the last 2 battles, cause the maximum health was limited to 99 (if there would be another harder difficulty, nme's would have dealt as much as damage with one hit, that would have messed up the game. That fact is proving the not arena-suitable tactical-engine.
5. Conquering a special field mission never worked for me. Somehow it never counted the field as taken, even endign the turn. I always had to kill everyone between the roundlimit.
6. I dislike the fact that some plants are destroyable, and some not, although the look alike. You can only differ them by searching with the mouse-pointer. Or is there another way?
7. The nme-healers do healing without any tactical calculation behind. They even heal if there is no hurted ally is around.
8. I dislike the fact that you are forcing players to go to ArmorGames to get the full content, especially if you don't make an early hint for that
9. Maps are getting to small (make them scrollable to boosting up the opportunity to make interesting levels
10. didn't got the point for my Spirit with that life sucking thing. t dealt too less damage in comparison to the normal attack (especially later i nthe game) and did not raised the health of the Spirit
11. although some things were changed and enhanced, it doesn't seem to be one hell of an efford to make this game (some maps and new characters), because you surely just reused your engine from chapter 2 instead of remaking it for really new features. Am I right or not?
Finally, it is still entertaining. But mostly because an experience-system and RPG is always challenging and forcing the peoples to collect and gather, leveling up their hero and his fellowhship. So you can't be so wrong after all with this.
But please, keep to a story RPG or introduce really new features - because you have the skill and your ideas the potencial to make a good game. Don't waste your time - I will be waiting for an astonishing, and hopefully with new ideas freshed up, chapter 3 of the story game.