A swordsman with YIP and technology, causes the archers of the wall do not hurt the attacking troops ... and an attack with elena and priests, the spiders of the wall are totally useless.
this is simply wrong. yips tailwind is limited in x and y dimensions. even if you play him on the front part of the field, it will never reach the wall.
regarding the siege aspect: i do see lich whales being really effective at clearing garrisons: bronze scorps and gold spiders clear the fields of lvl 13 troops with max research (obviously very strong heroes required). with the scorps change, not even all bronze(!) scorps die before the full field is spammed with spiderlings which are the best tanks in game right now.
to be fair: lich is really bad at plundering loot.