latest dev blog talks up The Elder Scrolls Online's
keeps and the design and engineering know-how that went into producing them. The devs wanted the game's three-faction PvP battles to "consist of multiple stages, allowing the attackers and defenders to each have several opportunities to turn the tide of a siege."
Keep layouts were planned accordingly, and player abilities like knockbacks, gap-closers, and AoEs factored in as well. Read the full blog at the official ESO