I’m not as up on IPL as I’d like to be, to be honest. Mostly because it frequently bounces around the TV packages up here, so it’s not always easy to find (or even available, if you don’t have the right one). This year I’ll probably watch more since it’s going to be on a package I have - and I am still unemployed, after several months of job search in a not particularly great climate for finding work, so will have the time to look at some. Most of what I pick up on IPL is off podcasts to be honest, so some of this is second hand, and some of it cursory looking at scorecards.
Mentioned up thread that RCB always go big on batting in the auction, and they frequently don’t perform well in IPL. There’s definitely a theory of the auction doing the rounds that, actually, it’s far harder to find good quality T20 bowlers to take wickets and limit the opposition, so better to spend big on those as it’s where you’ll get better variation for your crore. That theory could be taken into the game itself - cover yourself with more bowling options, hope that you’ve got enough batting to set a decent target and then defend it.
A look at Chennai or Mumbai from last year though and their team composition for the sharp end of the tournament had:
Chennai - Dhoni keeping and then 6 players bowling and 4 players batting. BUT - two of their bowlers were Ravindra Jadeja and Dwayne Bravo, both of whom are all rounders, so provide further security down the order should it be needed.
Mumbai - De Kock keeping and opening, and then 6 bowlers and 4 batters with Krunal and Hardik Panda both being all rounders, again to provide some security down the line up.
These teams got to the final and they are not set up too far away from a traditional side - the extra all rounder instead of a batsman being the variation on what England, for instance, would pick for a Test match (obviously, if you’re a 4 bowler side, the difference is more marked). I think it seems sensible that you want 6 players who can cover your bowling, in case someone gets hammered and you can avoid the risk of them bowling more, or play a match up and still have some flexibility with where your bowlers will bowl during an innings.
Obviously, your wicketkeeper must be able to bat. No one is going down the route of a specialist wicketkeeper #11 - and I expect they won’t, to be honest, despite my using it as a hypothetical up thread. Arguably you’d need 3 bloody good all rounders to cover a guy who won’t bat or bowl and still balance your side properly.
Essentially, it seems that all rounders of the ilk that Merrick suggested earlier - able to get through 4 overs and go off for 24 off 12 - are pretty critical to the balance of your side. Without them, you almost want to be going bowler heavy and hoping like hell that your bats can stay in and score quickly, which is definitely putting all your eggs in one basket. The way these successful sides are built though, you still probably need, at minimum, 2 gun bats and a good wicketkeeper bat, and 2 bowlers who can perform well in the PowerPlay and/or at the death to stand any real chance (Mumbai had Bumrah and Malinga for instance).