Whether it's worth it or not depends partly on how you get the money.
If you sell off ~20 dragonskins to fund your purchase of stronghold, the point at which it's worth it is when you start out with about 220 dragonskins.
If you have cash on hand, the question is whether you'll buy stronghold or buy ~15 dragonskins. In that case, it's better to buy stronghold if you've already got about 150 dragonskins.
The other possibility that I've been using to navigate is to get the page names, e.g. ...armoury.php, ...base.php, etc. in the pull-down address bar of the browser.
Then if I don't want to hunt for a button, I can still get to the page I want easily.
It would be fine if they introduced size attack limits, so long as they're not asymmetric like they were in Age1. It sucked to have some guy 1/5 your size attacking you regularly, but there was nothing you could do about it.