High latency during parties

When I play solo I normally have around 25ms , as soon I get in a party or some one join my grp latency reach sometimes 200ms and make the game quite laggy

Is any one having same problem ?

P.S : I have tested my connection with other game and is fine.

It can stick you in another region's instances if you're grouped with someone from that region. There's no "border" between regions, just you'll only ever auto-join (by entering the game, TPing, moving into a new zone etc.) the ones for the region you've chosen in the login screen. When joining someone else's group and going to their instance, you'll be put into that region's server.

If you want to avoid that, just create your own instance of the zone by holding down control when clicking on the waypoint/doorway/cave/whatever. This of course requires that the other group members join you by going to your instance via TP or clicking on the zone entrance.

Personally, I find that there's no visible difference between EU and US despite US being about 100ms higher than EU for me. The Singapore server is worse, sitting at about 300ms and causing a fair bit of lag. PoE seems entirely playable at ~150ms, and some high-profile hardcore players like Nugiyen plays on a foreign region at like 150 ping without any issues.

So basically, when you join a party and take a guy's TP, you'll enter an instance that might sit on a different region's server. You can avoid this by starting your own groups and being the one who creates the instances (by going to the zones first) or you can try to group only with people from your region.