I don't disagree with the basic point you're making, but I still think that HM LI is in fact a great example.
It is possible to undergear mechanics-based content in TOR. It's practically impossible to underskill that same content.
Unskilled players cannot do HM LI even wearing full Dread Guard. It doesn't matter how much mitigation you have, how many cooldowns you pop, how much hp you have and how much +power your healer has. Miss too many incinerates without a cleanse? Tank dies, group wipes.
Another example would be HM EC. Give a skilled group of players Rakata and they will finish it. Give an unskilled group of Players full Dread Guard and they will wipe.
Skill will let you undergear content. Gear will only let you underskill EASY content.
It's just as fair to say, "Unskilled players cannot do HM LI even wearing full Dread Guard," as it is to say "Skilled players cannot do NiM EC wearing full Tionese gear." And HM EC was balanced around Rakata gear, that's why it was clearable in the first week. Remember when guilds who weren't in full BiS with full augments tried to do NiM EC on the PTS and got rolled? Yeah, that's cuz of gear. You can't tell me there was a skill problem.
Skill compensates for lower than average gear just as much as gear compensates for lower than average skill. If Tionese gives you about 60% as full Dreadguard you're telling me what someone who is 60% as skilled as the best skilled ToR players can't do HM LI in gulld BiS gear? I highly doubt that.
You're assuming that Tionese is considered 0-level gear so you're comparing it to 0-level skill (i.e. "Derp, Derp, I don't understand what aggro means."). That's not a fair comparison.