Most of the boss weapons are not that great. Some are worth using for making a cool weapon/shield, but I would say, by and large, using them for souls is a better use for them. Soul of Sif can be useful for the shield, and some people like the furysword from Quelaag. Otherwise, there are much better items out their for the most part. Some of the DLC boss weapons are pretty cool though.
Purge is really good for learning pretty basic ways to play heroes effectively in the current metagame. However, once you have a decent understanding of the game, you should watch merlini. He doesn't explain himself as much as Purge, but he definitely plays at a higher level, and exhibits really good efficiency that nearly anybody can learn from. He doesn't post on youtube much, but he streams pretty frequently, and the streams are always archived so there's that. Here is his stream
Also, don't go too deep into either players catalog, dota is an evolving game and some strategies become dated and/or nonviable as time goes on.
One nice thing to know about those gargoyle's is that they don't have poise. This means that any hit will stun them. Try and agro one at a time, draw them in close, two hand your uchi and don't stop swinging until they die. I like to roll with < 25% equip so that you can more easily dodge their attacks, since their lightning attacks do quite a bit of damage through some of the more common medium shields (balders, hollow knight, heater).
Also, I have been able to knock the center one off of the perch using simple bow and arrow fairly consistently. I suggest that to thin out the herd a little bit. Agro the rest one at a time using the bow and you should be golden. Just note that you are about 5 minutes of solid gameplay from the most frustrating (for most) part of the game. Let us know if you need help with that part.