The game isn't well balanced and there are currently no plans to change that for vanilla Strive. While I took on the role of polishing up the game, it was my intent to minimally re-balance or re-imagine the game. In effect, balance was an issue left for mods to decide. Most mods make the game even easier and less restrictive, but a few add more challenges and restrictions. Unfortunately the biggest mods do not play well with each other(including Chastity Belt), but for different balance check out Aric's, Ralph's, or Leo's mods. Note, the first two only work for v0.5.25 so they provide their own game downloads, though Leo's only works on v1.0a.
Invigorate is hardly significant in terms of imbalance. Neither energy nor stress are required to significantly impact play and can both be mostly ignored until relevant moments like ending the day, so regardless if you spam Invigorate or not it is possible to exploit those systems. On the flip side, there are almost no penalties for simply ending the day to recover energy or spamming it generate infinite gold/mana from slave jobs.
Stat points on the player in vanila simply build up once you are maxed out, though being able to spend them on slaves is often considered part of a massive balance problem. The mods listed above change stat point systems in various ways, though I don't remember if they effect the player character's points.
You mention that you are using version 1.0a of Strive, but using Strive-1.0d-Bugfix-V2. Perhaps you misstated your version or perhaps that happens to work(I haven't tested), but it was only intended for v1.0d and could easily break stuff in other versions. Besides that, 1.0d fixes many problems in 1.0a, and is currently available despite the site saying 1.0a is the current version. Both mutation and slave turn-in quests were overhauled. If you still have problems with the Mutation spell in version 1.0d(with bugfix), feel free to give more detailed reports. I expect that biggest remaining problem would be the specialization requirements.