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When Baldur's Gate 3 came out, Steam's overall bandwidth consumption went from around 18 Tbps to 146 Tbps
(reddthat.com)
From Steam's self-published stats.
Baldur's Gate 3 could not be preloaded and weighed in at 125 gigabytes on disk, so when the game left Early Access at 11am US Eastern yesterday, Steam's bandwidth utilization shot up 8x over a span of 30 minutes. I know personally, I saw my download hit over 600 Mbps across a 1 Gbps fiber connection.
Kudos to the system engineers at Valve. It is mind-boggling that they have built infrastructure that robust.
XCOM meets Diablo is a decent enough way of putting it, as long as you don't expect the mechanics to be 1:1. Since you brought up positioning, there's no grid for movement, or flanking, for example. Battles are turn-based, like XCOM, but it's not split in player turn and AI turn, instead, each individual character/npc gets its own turn, with the order decided based on dice rolls and whatever modifiers are applicable.