The role reversal buff makes the champions behave as if the class relationships were backwards. So normally Skill has the class advantage over Science: when you fight science with skill the skill champion gets a buff to attack (it gets higher) and the science champion gets a debuff to attack (it gets lowered). With role reversal, the skill champ would get the lower attack and the science champ would get the higher attack.
So yes, in this case Stark Enhanced Spiderman would ordinarily get an attack penalty when fighting Heimdall, and Heimdall would get an attack bonus. But with the role reversal node, Sparky gets the attack buff and Heimdall gets the attack penalty. This is *not* generally shown in the panel: it will look like Sparky is getting the penalty and Heimdall is getting the benefit, but that's because this reversal doesn't take effect until the fight starts.
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So yes, in this case Stark Enhanced Spiderman would ordinarily get an attack penalty when fighting Heimdall, and Heimdall would get an attack bonus. But with the role reversal node, Sparky gets the attack buff and Heimdall gets the attack penalty. This is *not* generally shown in the panel: it will look like Sparky is getting the penalty and Heimdall is getting the benefit, but that's because this reversal doesn't take effect until the fight starts.