OK, so it would be merciful for God to let every evil person into heaven to torture his people forever? I would think it would be better to separate us.
I am not sure it is forever as you say, some believe death to be hell and the death of the unsaved is forever, others believe there to be a purgatory, where you will be punished for a time according to your sins. Whatever, I believe something will happen, but, it is not for me to know at this time.
Also, it could be as you are saying, but I feel it could be as bad as you say even if God was not responsible for its sheer unpleasantness. It says the unsaved will be separated from God. If you take all the worst people and put them together forever, don't you think that would be sheer torture, without God having to enhance the pain? Some believe a spirit cannot be killed even by God; it lives forever, wouldn't that be bad if a murderous person kept killing you and torturing you and you never died?