Sure its bound power but only for some moments to win map controll fights or to defend rushs & not for a complete PvP Match.
Mortar is great against nature defends,for cliffs & frost rush/defends. (Offensive/Defends)
beijingguy played primal defender..Ok, he played werebeasts & manawing aswell.
Ice Shield Tower & Wardens Sigal. Great to build up phase tower, canon towers, temite hills or mortars in closewell situations.
Last but not least the phasetower. This tower with most mobility can decide a T1 very fast. Defends/Offensive(No comment to church of negation)
Only a small overview about tower in PvP.
Sure there are isolated cases but overall towers are not underpowered and not overpowered in BF. (personal PvP view)