Interesting! Have a little look here - http://www.mkivsupra.net/vbb/showthread.php?t=306362
I'm convinced my top and bottom rad hoses are over pressurised too but the consensus of opinion is that it's normal. As said on my thread, imagine pumping a bike tyre to the operating pressure of your rad cap (in my case, 1.1 bar) it will be pretty hard!
Granted though, with your multiple hose failures and bulging joiners (although they look to be unbranded silicone jobbies!?) perhaps we both have a similar problem, just yours is more advanced!?
Not sure about yours, but it appears my coolant system could REALLY benefit from a thorough flushing. Possibly a build up of sludge causing blockage / excessive pressure? Though I'd still expect the rad cap to relieve this.