A couple of quick rule questions.

[Griogre]

Not to mention sliding or pushing if he was going to use a close blast. With some monsters you can see a secnario where a monster will interupt, hit and push a caster far away.

 

[Surgoshan]

2) Is there a penalty or chance of 'spell failure' in 4E if a Wizard/Warlock uses spell powers while wearing armor?

No, but anyone wearing armor he's not proficient in takes a -2 penalty to his attacks.

 

[Oldtimer]

Pg 268, under Immediate Action

"If an interrupt invalidates a triggering action, that action is lost."

It says "if". It's not an automatic thing. If the Wizard/Warlock merely takes damage, the spell will still go off.

 

[cdrcjsn]

It says "if". It's not an automatic thing. If the Wizard/Warlock merely takes damage, the spell will still go off.

Agree. Just answering someone's question about an immediate action invalidating an attack.

If the wizard was about to attack with a Melee Touch power for example, and triggers a push effect from his foe as an immediate interrupt, not only is the wizard pushed back, but his target is no longer valid so he loses that Standard Action and can't switch it to something else.

Likewise, if a warlord uses an immediate interrupt ability to move an ally to prevent an attack, the attacking creature can't switch it's attack to someone else. It loses it's attack.