Ok, here goes:
Bugs
The Escape button/“Back” function is not, uh, functioning: it does not bring up the main menu (like it used to), nor does it close any windows or return to previous menus. It did all these things - if memory serves - in pre-Gold versions.
Second, there’s no longer any way to preview future skills in a defender’s Skill Tree. If they’re not a high enough level, you cannot see what future skill(s) might do, nor can you see what level they become unlocked at. You simply have these mysterious, dim squares and circles in your Skill Tree - and if you haven’t played the game before, you have no idea what skills are going to unlock in the future.
Shouldn’t mousing over a future skill show a tooltip listing the power and effects of the skill at Level 1, along with Big Red Text somewhere saying “This Skill will unlock at Level X!”? Again, I swear this was in the game pre-Gold and is missing now.
Balance Problems
The Extreme version of Unwelcome Guests (normal game) is degrees of difficulty harder than the next map’s (Defend the Nest) Extreme version. After failing Unwelcome Guests on Extreme about 8 times, I took the same party (at the same levels) and easily defeated the next map - Defend the Nest - on Extreme.
You just don’t have the tools to deal with Splitting Mobs and Armored Snails coming at you from 3 lanes at once - funneling everything into a kill zone doesn’t work since there’s just so many monsters pouring in at once, and the splitting mobs have such a short path to Azra if you try to bottleneck everything into the lane where the others meet up, that they leak - even through multiple Blizzards!
And if you try to put Defenders over all three lanes, you simply don’t have enough Psi to have enough Defenders at a high enough level of Boost to kill even 2/3rds of the monsters in any given lane. I’ve tried every strategy I can think of, but they all fail and I feel I’m forced to level up and come back - which would be fine if I hadn’t stomped the next map in sequence into the ground at my current level.
re: Shock Lightning Book
TRIPLING the cost of the spell in order to add a 50% chance to Stun? That’s not worth it. Maybe if it also gave a small damage boost I could see it, but currently I find it’s better to simply run without a book at all versus using that one. 30 Psi is a significant investment when you first get this book (and for quite a while thereafter), and to only have it confer a 50% chance to stun a single enemy? I don’t see that as being a fair trade-off. Raising the cost to 15 or 20 Psi? Sure, I guess… just not 30. That’s way too high for something that your defenders get as a passive ability.
Even as a “gatekeeper” skill, trying to catch leaking mobs, it will drain so much Psi - especially coupled with the Psi Burn - that you’re really shooting yourself in the foot and costing yourself significant Psi and future Defender Boosts by using it more than once every few waves.