A full circle of women used the Bowl of Winds, and the BoW drew much more Saidar which made them visible to the Seanchan in ED...

the Seanchan see this amazing display of power and send 100 soldiers and six damane... Did the Seanchan want their soldiers to die? These damane to fail? What hope of success did the Seanchan predict?

A couple of possibilities, perhaps:

 

1) The Seanchan were able to determine that it was the work of a ter'angreal, using the Power, versus an angreal or sa'angreal, amplifying the power--and thus assumed that 6 battle-trained damane, with a military escort, would be able to handle even twice their number of "barbaric" Westland channelers.

 

2) The initial force was merely a scouting or reconnaissance party, intending to take seize control of the situation, if possible, or report back for reinforcements if necessary.

 

Or there's always this one:

 

3) Bureaucratic incompetence or red tape precluded sending an appropriate force on short notice.?