Ah, correct me if I am wrong, but not SL batted first in every game so far in the WC?
(or at least against meaningful opponents)
I fail to see then how Arnold can be held responsible for SL losing. In the case of the game against India it was the partnership between himself and Dilshan that gave SL a decent total, it was the same against SA, and against Eng he scored 20 odd at almost a run a ball. I fail to see what more he can do. Your arguments may have cogence if SL had been chasing, but not in the case of SL batting first - if SL has had a low total clearly the blame lies elsewhere, not solely (if at all) with Arnold.
Again, in regard to Marvan. Marvan has a decent avg. but it is true that he is a nervous starter, often takes a while to get set, and is particularly vulnerable to the new ball early on. I know that he has been SL's test opener, but a look at his figures during his career will bring up a large percentage of scores between 0 - 9 along with some massive knocks once he is set. Furthermore, as EWS has said in the other thread bringing in Marvan so that other batsmen can make runs during the PP makes no sense at all. If anything it would make it harder for the team as only one batsman would be scoring substantial runs - and for a batsman who supposedly bats through the innings a SR of 67 is very poor indeed. Very, very poor. The last thing the SL team needs is Marvan thuttufying at one end, while a succession of wickets fall at the other in an attempt to keep up a good RR.
The problem is with the existing batsmen, and the weaknesses of the batsmen and the overall batting line-up. Marvan is not a panacea for this, and in fact, he would likely make things worse. The batting order is fine as it is, all that remains is for Sanga and Chamara to start scoring some runs again, and for Vaas to come to the party.