It's really all going to come down to what you want to hunt.
Sambar deer are no problem as there is plenty of public land to access but this also joins private property and you need to know boundary lines and unless your a local even if you are lucky enough to see one it will probably be fairly ordinary.My choice,get guided and bag something respectable,taxidermy costs the same for either.
With Hoggies you certainly do require a permit and these deer live in very specific areas,not sure of the current cost of a permit but fairly hard to get I believe.
The mountains that I can see from here are full of Rusa deer but near all is private property and short of using thumb screws permission is DIFFICULT.Matter of fact the current(?)Australian record was taken not 10mins.from my house in somebody's front yard.And im not kidding!!
I believe all buffalo are owned by somebody one way or another and unless you lay down big bucks it's unlikely you are going to be the owner of one.
A good friend of mine ownes property in central west NSW and has plenty of good deer and is hosting a Yank next season on a swap hunt type of arrangement.You would be amazed at what can be worked out depending on who brings what to the table

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So despite my ramblings,to finally answer your question about guides,sometimes it's not necessary but highly recommended at all times.
I wouldn't go over there unguided,shit,I saw Deliverence