I'm just curious, when leveling do characters ever earn the ability to have more than one passive slot? Like a defensive and and offensive slot that could each be filled with different abilities?

Yes and no. You can never get more than one passive slot at a time. However, as soon as you get multiple builds you can give each of them a different passive if you want and switch between them.

After a switch there is a thirty second cooldown before you can switch again. That limits the usefulness quite a bit, but you can do things like starting out doing maximum damage and then switching build to activate a defensive passive if you get in trouble.

About that, do offensive and defensive passives share a slot, or will there be one slot for each of those?

They share the same slot. There is only one slot.

The four different roles you can put your character into (one role at a time for each build) place different restrictions on what can go into the single passive slot. The balanced/versatile role allows any passive power in its passive slot. Offensive, defensive and support roles allow only powers from their own category.

You can use builds as a way of rapidly switching role, equipment, power tray setup, costume and passive slot use. However, you can only switch rapidly once, then you have to wait thirty seconds before the next change.

Note that unslotted passives are always active - you can have as many of those going as you wish.

I am confused on this point... I have shodow form and regeneration... so will only one be working at a time? What is the point of slotting one or the other? If I attack the dummies and shadow is slotted, it gives me the effect... would regen still activate in the background?

Could someone please elaborate on this point? What are some examples of these powers?

Slotted passives are passives you have to put in your passive slot on your action bar. They will say that they are slotted passives. These are things like Regeneration, Invulnerability, Defiance, Modular Self-Assembly.

Unslotted passives simply work regardless. They're called innate passives or some such in game. Telepathic Reverberation, Ionic Reverberation, and what not are unslotted passives.

Slotted passives tend to have active effects that work in and of themselves. Unslotted tends to have broadly useful effects or effects that otherwise enable other powers to do 'more' or otherwise produce synergetic effects' - Telepathic Reverberation for instance restores energy for every target that's held by a telepathic power in range. The fire equivalent heals the hero for every instance of Clinging Flames within range - Clinging flames being the secondary effect of all fire powers.

he might be pointing towards skills like Killer Instict wich the Munitions class has, its a passive skill wich does not require to be slotted to work...but most of them are slot required to work...like targeting computer and quarry and so on. you can only have 1 of them active. just read on the skill on the info part on it. it will say if it doesnt require a slot as either offensive or passive.