For a pilot with no complex experience, the multi training will take a lot longer than one with even 10 hours or so in a complex plane, especially one similar to the twin (e.g., Arrow to Seminole). The more complex experience, the better.
In addition, getting the ME rating and being a proficient ME pilot are two entirely different things. If you doubt that, just ask the school at which you get the rating if they'll let you take the twin out on an overnight solo XC an hour after the examiner signs your Temporary Airman Certificate. I could probably stuff someone already complex-proficient through a ME rating practical test with a tame examiner in 6 hours, but that person would not be safe for solo in a twin. A more reasonable program to turn you into a light twin pilot (as opposed to merely the holder of an ME rating) would be about 18 hours for an experienced complex pilot and 25 hours for one with no complex experience.
Also, "high performance" means an airplane with "an engine" that is rated at "more than 200 HP." Seneca I's with IO-360's rated at 200 HP are not high performance ("more than 200 HP"), but the Seneca II+'s that have engines rated at 200HP at sea level and 215 HP above 12,000 feet are. Also, if you had a push-pull plane (I can't imagine this working any other way) with a 250 HP front engine and 150 HP back engine it would be high performance ("an engine").