The gathering of mankind will be in al-Shaam not in ‘Arafaah
Question

Will people be gethered on the day of Judgement in Arafat?
Praise be to Allah.There is no saheeh evidence to indicate that. 
Shaykh Sa’d al-Humayd 
Rather it is proven in the saheeh hadith that the gathering will be in al-Shaam (Greater Syria, including Palestine). It was narrated from Abu Dharr (may Allah be pleased with him) that the Prophet (peace and blessings of Allah be upon him) said: “Al-Shaam is the land of the gathering and the resurrection.” (Narrated by Ahmad). 
Al-Manaawi said in Fath al-Qadeer: “i.e., it is the place where the people will be gathered for the Reckoning. They will be resurrected from their graves then they will be driven to that land. It has been singled out for this because it is the land of which Allah said (interpretation of the meaning): ‘the land which We have blessed for the ‘Aalameen (mankind and jinn)’ [al-Anbiya’ 21:71].  Most of the Prophets were sent from that land and their laws spread throughout the world, so it is appropriate that it should be the land of the gathering and the resurrection.” (Fayd al-Qadeer by al-Manaawi, vol. 4, p. 171). 
But the gathering of the people on Hajj at ‘Arafaah reminds the Muslim of the gathering of all of mankind for the Reckoning and requital (reward or punishment).
And Allah knows best.