I have shared my thoughts on this here:
I came to a similar conclusion. We may have overestimated the Triglavians ability to attack a target system. However it seems once they have established a foothold in a system they are able to create stable connections to their space.
In every System they attack it starts with the conduits. If we could find a way to disable their ability to open those, they would be unable to enter our space. I’ve heard about technology like cynojammers or systems that manipulate spacetime in capsuleers empire nullsec to “attract” wormholes. I think this already existing technology is a good way to start creating a device that blocks the formation of Triglavian conduits.
There were also some cases where the Triglavians may have used Stargates to invade neighboring systems (see Raravoss)
However in Aldik they make no attempts to attach neighboring systems.