My own and others’ experience with Triglavians- in invasion systems and with roaming scouts - indicate hisec is less safe than prior to their introduction. Within the new player context of this thread, IMO Triglavians are a bit OP.
I’ve yet to encounter their “diamond rat” brethren, but hear they’re also likely beyond the ability of brand new players on their own.
Regarding potential danger from fellow capsuleers, I’m still regularly scanned by Tornadoes while hauling along trade routes, and there’s never a shortage of flashing, red, criminals and wrecks at gates and hubs along said routes.
I’ve only played EVE since 2013, so cannot speak to the hisec danger level prior.