DotA 2 is always striving for balance, as much as it can be achieved. That sometimes works, and sometimes it doesn't. Let's talk about five heroes that may just be too strong and the cases where balancing kind of failed.
As number 5, we see the return of Axe. His Counter Helix now deals damage pure damage instead of physical, the damage was reduced a bit but this is huge for Axe. This means that armor and block mechanics won't work against it, making carries buy BKB just not to kill themselves while attacking Axe. Blade Mail also got an update and now it returns damage before any kind of reduction is applied.
Lifestealer is number 4, and his buff is small, but the impact it makes is quite large. His strength gain is now 2.4 to 3.0, giving him 300 extra health and 15 damage at level 25. Armlet also got a buff and now with Unholy Strength it grants 5 armor. Lifestealer with an Armlet will pretty much be unkillable unless he faces a lot of physical damage, and even that it will have to burst him down fast to negate his life steal.
Slark takes number 3 even though he never really received any direct buffs. Silver Edge’s got a new recipe, now involving Ultimate Orb which is an absolutely crucial for Slark, who is heavily dependent on acquiring stat items. Echo Sabre, which gives a double attack every five seconds is also making some pretty broken builds, but none are final, so I can't really say if they are going to nerf them or not.
Lich takes the number 2 spot with his changes to his Frost Blast and Chain Frost which makes them independent debuffs. This makes is so that landing his Frost Blast makes it easier for Chain Frost to perma slow people, making them move so slow that they might as well be stunned.
Dragon Knight is number 1, with two more buffs to him. Breathe Fire's attack damage reduction is now 35% at all levels and his base damage is increased by four. This makes his laning much better, allowing him to transition into that mid-game monster, and the Armlet buff will only make this dragon hit harder!
These are my current suggestions for DotA 2 heroes that could probably do with a nerf, but I am sure you guys got other ideas so please share them in the comments section below.