It's more accurate to say it like this:
If a single ability is overpowered, it should be looked at, but if it doesn't make the hero in general overpowered, it's not a high priority. It's something you should keep in mind, but it's not OMFG FIX NAO.
If the entire hero is overpowered, that's your priority - there shouldn't be any heroes that are always going to be a first-round pick/ban in nearly every game simply because of how ridiculously strong they are. I don't know if it's possible to prevent this from ever happening, but when it does happen, action should be taken.
For example, Batrider was seen in 428 of 428 tournament games played, according to the stats someone posted last week. So why was he picked or banned in literally every single game? Is he overpowered? If he isn't, why is he still being seen so often? If he's determined to be overpowered, what are your options for bringing him back down to earth?
You could maybe do the same thing with heroes, looking for heroes that are underpowered and might be in need of attention - I think you could make a case for both Morphling and Invoker here, though it might be that neither hero is underpowered, just not suited to the current playstyle. Likewise, just because a hero is seen frequently doesn't mean he's overpowered... though it can be a potential red flag.
I don't like a stagnant metagame. I think making small, incremental adjustments to heroes that are overperforming is a way of encouraging different playstyles without doing something ham-fisted like post-TI2 nerfs to Morphling and Invoker (neither hero is seen much anymore because of how enormous the nerfs were to them.)
Honestly, I'd really like to see relative hero strengths be based around the amount of skill or APM required to play them; I hate how strong Leoric can be despite being almost certainly the easiest hero in the game to play (you have literally one button to push and you typically don't even buy items with activated abilities on him!), same with CK, PA, etc etc etc. I don't think Dota is designed in a way that would make basing the game around that feasible, but it's always annoying to see someone that has no idea what they're doing still perform very well because their hero doesn't really require you to know anything about the game.
Then again, my favorite hero is Visage and it's disheartening to push my APM to the limits and perform at the same level as someone that's spent half the game watching TV on another monitor
---------- Post added 2013-05-10 at 01:29 AM ----------
Juggy's crit, while RNG, doesn't bother me because he's not going to slice someone in half with a single swing unless he's ridiculously fed. All PA needs is phase boots and a Bfury to get to the point where she can very easily one-shot supports and even the squishier carries.
PL is boring as fuck to play and watch but I'm not sure I consider him overpowered. I'd like to see his illusions benefit less from Diffusal Blade than other illusions, but that might relegate him to "never played" status. Without a gigantic army, he's actually not that great at killing people compared to other carries - I guess his real use is in how rapidly he drains someone's mana with eleventy billion illusions all hitting at the same time. Nerfing that too much might make the hero irrelevant. I do think the whole "slow siege" thing with Manta Style and the army is pretty fucking stupid, but PL needs to be pretty fed for that to happen. I'd guess that if you let PL get that fed without having a way of dealing with it, you deserve to lose anyway.Cancer lancer also needs some adjustments. Its not conceivable to have to send a minimum of 2 heroes to follow him teleporting around the map to stop his stupid farm.
It can be interesting when it's not 45 minutes of AFK farming every game. I liked watching the pros use Replicates to maximize Morphling's farm time in TI2, but it got boring when every single game was like that.Also how do people feel about farming? I know its part of the competitive scene but I really play this game for the team aspect and for the excitement of outsmarting and outplaying other living breathing humans.
Farming AI controlled creeps for 45 minutes then coming out at the end of the game and roflstomping everyone is booooooring.
I guess it's unfortunate that Dota's meta seems to be pretty static without outside influences encouraging teams to try different playstyles. I wonder if 4-protect-1 would've fallen out of favor to be replaced with the trilane meta if Valve hadn't broken Morphling's kneecaps with 6.75.