- Buyback prevents gaining unreliable gold until your normal respawn time finishes
- When buying back, 25% of the remaining respawn time will be added to your next death
- Offlane creeps meet closer to your tower
- Ranged heroes now receive same amount of denied experience as melee heroes (instead of less)
- Experience AOE is now 1300 instead of 1200
- Non-ancient neutrals now split experience with all heroes in the AOE instead of just the team that killed it
- Medium pullable neutral camp has been swapped with the small camp
- Pull timing duration has been reduced
- Jungling has been nerfed (experience gain has been lowered on almost all creeps)
- Day and night time is only 4 minutes rather than 6
- Roshan now respawns randomly between 8 to 11 minutes
- When aegis expires unused, it heals the hero fully over five seconds
- Random gold bonus has been reduced by 50
- Gold for ending a spree has now changed from 75 to 600 and 125 to 1000
- Gold income is now 1 per 0.6 seconds instead of 0.8 seconds
- Tower last hit bonus has increased from 100-200 to 150-250
- Melee barracks now regen at 5hp/s and ranged barracks no longer regen
- Ranged barracks now have 1200 instead of 1500 HP and armor has been doubled to 10
- Evasion stacks diminishingly
- Can no longer orb-walk with ethereal blade (fucking Huskar)
- Wards give 50 gold on destruction
Those are the bigger gameplay mechanics that have been changed.
Bloodseeker on the other hand has had his movement cap removed. Yes, he can now move at like 1000ms. That and thirst is now map-wide with vision cap at 50% across all levels and stacks infinitely. He will be a popular pub pick choice.
The new four minute cycle of day and night can swing both ways for Nightstalker. He's definitely more useful consistently for ganks, and Nightmare now reduces enemy vision by 25%.
Slark's shadow dance can now no longer been seen even with truesight.
Pudge/VS can use blink dagger.
Invoker now regains 50% of the mana dealt with EMP and has 2 spell invokes at Level 1 instead of 2.
Lich sacrifice cooldown has been increased, but now grants experience in an AOE. Also, it no longer denies experience for your enemy.
Item-wise, linken sphere can be transferred, tangos are no longer shareable, shadow blade cooldown increased to 28 from 18, and tranquil boots have been reworked and can no longer be disassembled.
More here -
Fashionably Late: 6.79 Patch Analysis | DotaMetrics