Fair warning: this list is entirely subjective, as there are players who enjoy spamming heroes all day every day for months and seem to never get bored. Certain heroes are more fun to play than others, and some are more natural flashy playmakers. However, the relative fun/boringness of heroes is also somewhat dependent on the state of the meta and their viable roles and builds.
Heroes with stagnant builds
Icefrog giveth, and icefrog taketh away. Sometimes, the meta doesn’t leave you with a ton of build options, and when that happens, heroes get boring to play and play against. If your Sven is building into a Mask of Madness every game, that gets pretty old.
Micro-heavy heroes
Some people really like playing Chen. These are probably also people who excelled at StarCraft. For me, micro-intensive heroes (looking at you, Meepo) get too repetitive after a while as I have to keep corralling my units.
Rubick*
Hear me out. Rubick is usually exciting and unpredictable to play, as you’re stealing your opponents spells and getting to cast a variety of abilities. Nobody would ever put him in a list of most boring Dota heroes.
But what if your opponents are only playing heroes with boring spells? Have fun stealing Plague Wards. That shit is dull.
Rubick is also pretty boring when your opponents don’t bother to skill spells.
Supports
While heroes in Dota are technically somewhat viable in every role, there are quite a few that have been relegated to support for the time being. I feel guilty saying this to all our valiant support players out there, but supports can be some of the most boring Dota heroes to play. They tend to have a pretty slow item and skill progression, which means that there’s less variety during the game for the player controlling the hero. Also, while they’re indispensably important in actual gameplay, they don’t get a whole lot of the flashy moments of glory. It’s kinda like being a libero in volleyball – there to watch everyone’s back, but rarely creating Kodak moments.
Again, this is all pretty subjective. You might love playing support heroes or spam Meepo like there’s no tomorrow, and who am I to take that away from you? But the most boring Dota heroes question is asked a lot on the internet, and a couple of heroes seem to always make the list: Dragon Knight and Viper. For DK, this mostly has to do with a long-cooldown ultimate that makes him a little dull. His playstyle boils down to “become dragon, hit buildings, wait, become dragon, hit buildings again, wait.”
In the case of Viper, his four abilities are all fairly similar. The first two add a damage bonus and a slow, the third ability damages enemies nearby, and his ultimate… adds a slow and deals damage. Snooze. No summoning units, no roots, no heals… just damage and slows. All day, every day.
Dota has the benefit of over a hundred different heroes, all of which are playable in some form or another. But let’s not pretend that all of their abilities and playstyles are a slam dunk in the fun department.