First of all, see here what backdooring actually is.
Tier 2, 3 and 4 towers and barracks have backdoor protection, which causes them to regenerate 90 hp per second and take only 25% damage from illusions if they are attacked without enemy creeps nearby.
So in order to backdoor successfully, a building needs to be low enough to be destroyed in a single hit, or the hero needs to be able to make more than 90 damage per second which after added damage reduction(armor) from tower which is ~ 55%-65% depending on the tier...you would need around 240 DPS to make the minimum impact on the tower,and since enemy team will rush to stop you as soon as possible you will need a lot more damage.
This is generally very difficult for most heroes for most if not all of the game, with backdooring typically being a team effort,single-hit destruction or mostly beneficial ability or item on your hero.
Things to look for in a backdooring hero:
- High DPS - To overwhelm the BD protection you will need a lot of damage and attack speed, late in game many heroes can do it but earlier it makes for a big problem.
- Mobility - You will have to get to their base quickly as possible and/or unseen to avoid enemy team defending.
- Summoned units - They can be good way of backdooring since you don't have to put yourself in danger, but rarely have enough damage without hero contribution.
- Items - Boots of Travel, Shadowblade, Necronomicon, Manta Style, Helm of the Dominator, Mask of Madness or just a lot of pure DPS items.
Popular item choices to help you with this are Desolator(damage+armor reduction) and Necronomicon (DPS+extra creeps).
- Nature's Prophet - Teleport,spawn treants,DPS
- Lycanthrope - Very fast,DPS
- Lone Druid - Summoned bear deals a lot of damage to towers with his passive, DPS, tank
- Leshrac - Diabolic Edict deals huge damage to buildings if no nearby units
- Clinkz - Fast invisibility, DPS
- Troll Warlord - Only crazy DPS
- Phantom Lancer - Lots and lots of illusions, invisibility, DPS
- Death Prophet - Fast, ghosts can destroy buildings quickly
- Broodmother - Partial fast invisibility, broodlings, DPS
- Meepo - Can simultaneously defend and backdoor as needed using poof, DPS
- Warlock - Powerful golems that can tank and destroy
- Faceless Void - Chronosphere stops towers, DPS
- Chaos Knight - Fast, strong illusions, DPS
- Tiny - Huge damage, +75% to buildings with scepter
- Shadow Shaman - serpent wards
- Chen - Enchanted Creatures can tank and pack some DPS,depending which you take
- Enchantress - With DPS build and enchanted creatures to tank
- Razor - Eye of the storm does lots of DPS to towers since every hit reduces armor,with aghanims 2 storms can be active at the same time