If you're already certain you have IO contention, start by understanding which files are the cause.
DB_NAME(fs.database_id) AS [Database Name]
, CAST(io_stall_read_ms / (1.0 + num_of_reads) AS NUMERIC(10, 1)) AS [avg_read_stall_ms]
, CAST(io_stall_write_ms / (1.0 + num_of_writes) AS NUMERIC(10, 1)) AS [avg_write_stall_ms]
, io_stall_read_ms + io_stall_write_ms AS [io_stalls]
, num_of_reads + num_of_writes AS [total_io]
, CAST((io_stall_read_ms + io_stall_write_ms) / (1.0 + num_of_reads
+ num_of_writes) AS NUMERIC(10, 1)) AS [avg_io_stall_ms]
sys.dm_io_virtual_file_stats(NULL, NULL) AS fs
sys.master_files AS mf
ON fs.database_id = mf.database_id
AND fs.[file_id] = mf.[file_id]
With the data from that query you can judge whether the log or data files are the point of contention in tempdb. It's probable you'd be better off with both data files on one drive and the log file separate, but you'll never know without the numbers to back the decision.