SCTP can detect failures on alternate paths through losses of heartbeats. And yes, SCTP does not allow load sharing over the multiple paths, but with good reason.
There has been work on improving failure detection and handling Concurrent Multipath Transfer (CMT) with SCTP.
See: http://pel.cis.udel.edu/
Your intuition that solving the load sharing problem would go towards solving the failure detection problem is right on.
I agree. See (upcoming) paper at WWW 2006 which talks about why SCTP is a much better fit for HTTP as compared to TCP:6 .www.natarajan.pdf
http://www.cis.udel.edu/~iyengar/publications/200
Your intuition that solving the load sharing problem would go towards solving the failure detection problem is right on.