From what I've seen, icewall is just another part of the competitive element in mvp defense. The reason why Azviar held it so long there in this particular instance was because Bryjar was outnumbered and had poor class composition. The team was composed of mostly champs (that mostly just body reloc for the boxes), hps, some snipes and 1 hw. Moments after these screenshots, more Bryjar members came in who were hw's and also a prof who quickly diffused the situation with sight thrasher and LP spam. From then on, it was pretty evenly matched. I don't think it would be good to block icewall on the map, as there are several ways to counteract it and would otherwise eliminate another tactical option people can take (it's used to block people from the mvp in the open field, not just the corner as depicted here). It's also difficult to lure the mvp into the corner in the first place since it keeps swapping aggro from several dps - again the reason why this happened is cos Azviar's hps reacted quickly and because of the reasons above (outnumbered/composition).
Also, I second what Cheron said. It's sad that hps and classes that do all the work to defend and heal the mvp get nothing, compared to people who just run around and hit the boxes without contributing to the actual fight and reaping the rewards all for themselves. By the time we finished the round, one of my friends who's new to the event and hped for the entire hour was like "What?? How come no tickets??".