Yeh unfortunately you do get people who can't let go of their ego and do silly stuff like dropping people on their heads. Letting go of the ego is a massive part of it, most of the time rolling should be about learning rather than winning.

Absolutely right conditioning is soooo important. If you're tired you get caught in all kinds of shit that would never happen if you were fresh. With some fundamentals + good conditioning even relative beginners can be a real handful.

For MMA I would say the most important things to get good in first are:
Takedowns, positioning, sub-defence.

If you want some inspiration for training I suggest:
‪Genki Sudo in Westside Tournament Original Full version (2001)‬‏ - YouTube