
. No sir, the type of variations needed for bowling well in T20 int'ls is the variations needed to bowl @ the death in 50 over game. Many good/decent/very good bowlers in ODIs didn't have those variations, but that doesn't mean they where crap/poor.
To date in international T20 the type of fast bowlers/medium pacers or spinners who are effective are:
Fast/medium pacers - the ones If you have the yorker MAINLY, along with clever variations such a the slower deliveries, slower bumper - you will get smashed.
Alot of great bowlers in tests/ODIs didn't have these pre-requistes thus would struggle in this format. For eg swing bowlers like Hoggard & Anderson who ability to test batsmen by pitching the ball up are basically very ineffective in this format.
While in ODIs bowlers like Hopes who tend to do decent jobs in ODIs get smoked in T20s
Spinners the bowlers who try bowling quickly get smashed in T20s. But those same type of bowlers could be ecomical in ODIs. Only the spinners with great guile & variation do well in T20s.