It's normal IF the indexing on the data was not optimal, so that you were scanning old data before that has now been removed.
Note that when you DELETE a large number of rows SQL defers the actual release of the data pages until later. A batch process later removes these "ghost" rows in increments. For 1TB data, I guess it's possible that it took more than 2 days to completely DELETE the ghost rows.
You should rebuild the affected tables after that large a DELETE.
You should also review index statistics, including missing indexes and current index usage and table scan counts, to verify whether you need to re-index one or more of the tables.
SQL DBA,SQL Server MVP('07, '08, '09)
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