
Skill Systems and Runes
To start, he went over some of the skill systems featured in previous Diablo games.
In Diablo 1, the book skills were nice in that it was exciting to get random drops, but they also lead to a lack of character customization since everyone had the same skills, and increased difficulty for those who were unlucky in getting skill book drops.
The Diablo 2 skill trees allowed for stronger class differentiation and a wider variety of skills, but they certainly had problems as well. Trees encouraged you to focus on only a few skills, and some skills were built such that it was a bad idea to put in more than a point or two, while some were essentially useless. Because of this and the lack of a respec system, mistakes could easily "ruin" a character, and point hoarding was often a rule, once again leading to difficulty as people saved points for later leveled skills.
The skill system they are now working with is not completely done, but they feel it is on the right track. It's an evolution of the D2 system, with some of the same tree ideas. There will be a new focus on passive skills that provide general character bonuses, somewhat similar to D2 synergies. These will also be useful for bypassing levels of skill trees to get a skill you want in a higher tier without having to buy something you will never use.
Respecs are not designed yet, but they will have a respec system of some sort.
The new rune system was probably the star of this portion of the panel though. It's not like D2 Runewords though. These random drops actually directly modify your skills.
They drop with multiple tiers, with higher tiers granting bigger powers. They work for all classes, and modify spells in specific ways that are meant to be game-changing. They're also swappable, in order to encourage experimentation.
The Skull of Flame, a Witch Doctor Ability, gains the ability to bounce to multiple targets with the Multistrike Rune, while the Power Rune causes it to leave behind a burning area on the ground that damages enemies.

