As always, Valve is trying to rework heroes to keep the playing field both even and interesting. Many of the most-picked heroes, CM, Alchemist, Visage, and Venomancer, will all be taking nerfs.
Alchemist's Unstable Concoction now has a shorter countdown timer (charging for a maximum of 5.5 seconds instead of 7), only receiving max damage .5 seconds before he stuns himself. In addition, the stun will not receive additional damage while travelling to the target. Finally, his field of vision during night will recieve a 40% cut, making Unstable Concoction much more difficult to land and much riskier to begin without allies.
Crystal Maiden, Venomancer, and Visage will each suffer nerfing: base intelligence for CM has been reduced by three, Venomancer is down .5 hp/sec base regen and five base damage, and Visage movement speed decreased by five. This along with an early-level manacost increase for Grave Chill may make Visage, who typically thrives in high-pressure, early game environments, much less desirable.
2) Fixing the Broken
Broodmother's ability to walk off the map is about to end
Valve's next task in any patch is to try and address some of the "broken" hero mechanics. In this case, Broodmother: prior to this patch, she was able to immediately walk over terrain and even escape the legal boundaries of the map to avoid taking damage, making her nearly impossible to kill. Now she can only move over impassable terrain while not in vision (either due to fog of war or invisibility) and all heroes are confined to the boundaries of the map. In addition, her webs no longer grant vision, so say goodbye to free rune and Roshan warding from this hero.
3) Keep on Buffing
After receiving significant buffs in 6.79, both Axe and Bloodseeker will continue to be given additional strength. The DotA Gods seem to smile on these heroes: Axe is given a huge survivability boost with a 50% base regen increase (from 2 to 3) and Beserker's Call duration increase at every level (alongside a now 16/14/12/10 cooldown instead of a flat 10).
Bloodseeker's Thirst has been rescaled to be less in early game and more in late game, giving this hero more of a mid-game, semi-carry feel than he already had. In addition, his team fight presence has been hugely bolstered: any hero who dies within 325 units now gives full bloodbath benefit, amping his presence in these scenarios significantly.
4) Don't Forget the Others
Other heroes receiving significant changes include Earth Spirit (whose mechanics have been largely altered), Meepo (ult at level 3 plus reduced spawn cooldown), Ogre Magi (who now permanently has a secondary stun available with Aghanim's - regardless of its current mana), and Jakiro. The Twin-Headed Dragon was a long-time competitive scene favorite due to his strengths in early and mid game along with a solid AOE stun, but now Jak has increased Liquid Fire and Dual Breath DPS, along with additional buffs to Dual Breath and some other mechanics alterations giving Jakiro even more early game potential.
5) The Aghanim's Club
Finally, a few heroes will be given the strength of Aghanim's Scepter. Lion can down do Finger of Death damage in an AOE, damaging all enemy heroes within 200 units of the primary target.
Tinker's Agh's build will allow Laser to be cast at a staggering 1100 range and will cause Heat-Seeking Missiles to launch toward up to four targets rather than just two.
Gameplay Changes
6) Buffing the Big Boy
Roshan has taken some very significant changes in this patch. The mighty giant will no longer cease upgrading his HP, damage, and armor at 45 minutes, and these upgrades have been buffed by 20%. Late-game, match-deciding Roshan kills will now be more difficult and allow teams more time to react. In addition, his bounty has a higher minimum and a lower maximum, making a Roshan kill more stable in the way it impacts the course of a game.
7) The Hills Have Eyes
All wards can now be traded like tangos, allowing one support to buy wards and hand one off to another player. This will enormously change the nature of pre-game warding, as wards will be easily split across a map to different lanes.This can be done with Sentries and Observers, also allowing teams to counter-ward in one lane while providing truesight of invisible heroes in another.
8) Blink Dagger Forever
Blink dagger now has no mana cost, so Silencer, Nyx, necronomicon, Invoker, and other mana-draining fiends will be unable to prevent an escape without providing a source of damage.
9) The Team That Drinks Together...
10) ...Syncs Together
Finally, one of the most noticeable mechanic changes of the patch revolved around reaction time: team movement via Scrolls of Town Portal will be much faster. Prior to this patch, a team which teleported to the same location would suffer additional channeling time (3/5/6/7/8) which would prevent their ability to engage as a team. Now this channeling time will not be 3/5/5.5/6/6.5, rewarding teams which react en masse.
Source : Here
