In DotA 1, the heroes are organized into three attributes: Strength, Agility and Intelligence and 2 factions: Sentinel and Scourge. Will reusing all of these names mentioned will cause a new game to became a derivative work, even through these names are apparently generic? (Some games have distinctive attribute/faction names, but this doesn't appear to be the case in DotA)
Strength, Agility, Intelligence, Stamina:
Unlikely, given the vast array of prior art and the "Obvious to any practitioner in the field".
Virtually every RPG out there uses four familiar stats:
This is such a deeply held trope, and so axiomatic to RPGs on or off computers, that I doubt any intellectual property is in play. If it ever was, it has been completely undefended for the last 40 years, so it's much too late to now attempt to claim rights.
Sentinel and Scourge
Let me dodge that one and generalize: Can you use Alliance-Horde?
See, there's a real spectrum there! The four names alone are so unique that J.K. Rowling would come after you if you used them anywhere. But Empire-Rebellion is too generic to assert an IP claim over.
And if you pluck non-paired names from an IP, like Ravenclaw-Granger, that's not a problem either. A Wild West movie with feuding families the Grangers and Ravenclaws, would be absolutely fine; whereas Ravenclaws and Gryffindors would not be fine!
DOTA 1, however, is a copyright morass. Many games permit fan-created "mods", ranging from the TM:PE traffic modeling mod in Cities: Skylines to the TSM auction pricing mod in World of Warcraft. The mod is nothing without the game. The game author doesn't own the mod, The mod author doesn't own the game. They coexist mostly by consent.
DOTA I was an arena "mod" to Warcraft III and there has been quite considerable fighting over ownership of that IP. Valve now owns it but agreed to allow non-commercial use of the IP.
Even so, the Sentinel-Scourge pairing is only really important in DOTA I. The pairing doesn't mean much in Warcraft III, as they are disjoint, like my Granger-Ravenclaw example above.
You would probably be fine, but the risk of trouble is exactly why original games create original IP - for instance Sentinels-Scourge was not reused in DOTA II!