Basically any notebook with a dGPU can handle Dota yo
Just choose whichever you like!

Your requirements are too general to recommend specifically 

There are AP units for Lenovo, so do make sure you are not buying those if you still want the warranty
I can't tell, I'm not familiar with every buyer in the market
If you want, you can ask him to provide you with his successful tradelist, then you can ask some of his sellers and ask for opinions or comments

On the other hand, you can consider this one for your budget; if you don't mind the size, of course
15.6"
Dell
Inspiron 15R, i7-4500U + AMD HD8850M (GDDR5) @RM2499[2.32kg], 8GB, 1TB(5400rpm), Linux, 65WHr; W8SL@RM2699

Bro [putochip123] is selling this at a much lower price than RRP~ This seller I can vouch for haha
The AMD HD8850M is not as good as the GT755M, but the performance difference is not too far off: http://www.notebookcheck.net/Computer-Game...ds.13849.0.html
And for the price you pay, you don't have to stick to FreeDOS 

U are most welcomed~
Happy Purchasing~ 
Read here for more details: https://forum.lowyat.net/topic/3112306

there are plenty of them, those with physical shops or reputable ones are much more as an authorized reseller.

the stars means nothing. its just an essential rating for those whom posted a lot (or peoples whom spammed a lot).
and yes, versace is an authorized reseller. he has a physical shop at lowyat plaza.