Pace bowling in T20

From CricInfo's match report...

"While South Africa may not be entirely pleased with all elements of their batting, especially their middle order, their attack held them get out of jail. Tabraiz Shamsi turned in the most economical effort of his career so far (2 for 13 in four overs) while Anrich Nortje and Lungi Ngidi conceded 52 runs in seven overs between them and worked their variations well after West Indies seemed to be on course at 96 for 3 at the halfway mark of their 168 target."

I'm beginning to wonder if T20 requires a much different team composition. 

Bowling attacks between T20, ODI and Tests don't vary much. Not nearly as much as the batting anyway.

Without actually knowing the numbers, I'm betting that slow bowling is more economical overall.

Sure spinners do get blasted sometimes but, game after game, spin bowling does the trick in T20s. They don't even have to turn it that much. A combination of flight and little pace on the ball are enough to frustrate and panic batsmen.

Are T20 sides better off picking batters that can bowl some spin or slow-medium over all-out pace bowlers that do little else? 

for example, 

Boje - Bowler

Duminy - Bowler

Symcox - Bowler

Cronje - Bowler

Faf - Bowler

Keeper

Batter

Batter

Batter

Batter

Batter

TLDR; Would you give away more runs with this bowling line-up than the runs you would gain from it at bat?

This is only concerning T20 and of course just speculation.

EDIT; 

Duminy T20 Economy - 7.76 x 20 = 155.2

Dale Steyn T20 Economy - 6.94 x 20 = 138,8

The difference being 16,4 runs

Five batting all-rounders is worth more than 16,4 runs in an innings.

What am I missing?

It depends on the wicket, all the batsmen have said the wickets are difficult to bat on.....sticky, two paced are the words used to describe it. Even the home side has struggled throughout both formats.

Also there's a big difference between the Duke and Kookaburra balls, in this series they're using the Duke. With the exception of Quinton De Kock batsmen on either side have shown a lack of consi stency.

Denny,

The calculation I did above was using the lifetime economy rates of Duminy(an ok spinner) and Steyn(probably our best ever pace bowler) in T20.

So, I'm not talking specifically about this series. Rather, focusing on the broader question.

Cumon guys...tell me what I'm missing.

To my mind one would use two very different looking and performing vehicles in drag racing versus Le Mans.