I'd argue that if you're going to be spending an entire episode watching a relatively good guy attempt to contain the chaos in cities filled with infected people, you're going to be at least a little saddened by his death at the end. It doesn't seem pointless to me at all, since it's creative/intricate storytelling, unlike the contrived plotlines/character developments in season 2.

With the soldier in the tank story, you'd also get to see scenes containing average people unable to accept the idea that they're sick and won't get any better. People attempting to go along with their normal, day-to-day lives even though they're obviously unwell. The soldier's reactions to these people would've been interesting since we never really got an appropriate insight into what people were like when society was only on the precipice of falling apart and not already broken.

I think Darabont also wanted to include scenes that showed what Andrea/Amy/Dale and Glenn were doing at the time the soldier was attempting to restore order in the city.

It would've been a great episode lol.