Timeout in Bulk operation when deleting documents

I have a list of document IDs I want to delete.

The naive way works well:

foreach (var Id in IDs)
{
EC.Delete(Id);
}

but it is insanely slow.

So I tried this:

EC.DeleteMany(IDs);

which doesn't seem to do anything at all; it certainly doesn't delete the documents.

Then I tried the bulk approach:

var Bulk = new BulkDescriptor();
foreach (var R in RecordIDs)
{
Bulk.Index(_ => _.Document(new IndexedData { Id = R }));
}

And now this one fails:

"Invalid NEST response built from a unsuccessful low level call on POST: /_bulk\r\n# Audit trail of this API call:\r\n - BadResponse: Node: http://127.0.0.1:9200/ Took: 00:01:00.1360093\r\n - MaxTimeoutReached: Took: -736111.13:10:20.1704195\r\n# OriginalException: System.Net.WebException: The request was aborted: The request was canceled.\r\n at System.Net.ConnectStream.InternalWrite(Boolean async, Byte[] buffer, Int32 offset, Int32 size, AsyncCallback callback, Object state)\r\n at System.Net.ConnectStream.Write(Byte[] buffer, Int32 offset, Int32 size)\r\n at
...

So, the problem is a timeout, but this is on an idle development computer with elastic running on the same machine.

Could it be that bulk operation do no handle a large number of operation? (1.2million in this case).

Also, is there a better way to do this? creating an empty class for every command, just to put the ID in it seems incredibly wasteful when I could just pass the ID.

I have now broken down the operation into chunks of 5k records to test:

var Bulk = new BulkDescriptor();
            var Count = 0;
            IBulkResponse Result;
            foreach (var R in RecordIDs)
            {
                Bulk.Delete<IndexedData>(_ => _.Document(new IndexedData { Id = R }));
                Count++;
                if (Count % 5000 == 0)
                {
                    Result = EC.Bulk(Bulk);
                    Bulk = new BulkDescriptor();
                }
            }

but it is insanely slow as well: 10minutes to remove 1.2m records vs. 10-15 seconds when we used Lucene. What am I doing wrong?