Clan tech being better than IS tech is in the end, somewhat of a myth.
I've piloted both and am honestly better with IS tech.
They reflect different philosophies. Clan is glass cannon, IS is DPS workhorse.
Raven can tank an Uller easy but is going to take forever to kill it so it evens out. Take an Owens B against some ullers and see the difference in philosophy. Hell its even possible to solo the heavier Clan lights in IS lights if you have MASC and room to maneuver.
Scat vs Bushwacker? Same thing, sure the scat has comparable armor and is harder to hit, but its main firepower usually is all stuffed on one arm which once destroyed, spells the end of its effective role on the battlefield. Whereas the bushy (take the A or the E or the B) has spread out weapons, they are the same speed, but the bushy is no where near as maneuverable as the Scat.
To the heavies, a Thanatos can take on pretty much take on any clan heavy if piloted right. The Catapult is basically a better dedicated missile mech than the Vulture: JJs, armor, and pods in ears rather than torsos evidence this. The WH is sort of weak with its meh armor and slow speed, but it has lots of role options in the game now. Loki's have trash armor and can be easily taken out if you know they are coming.
The only real outclassing will probably be in the Assault category but we will see, the weaknesses of Assault are being SO DAMN SLOW and most clan assaults share this problem and the amount of weapons they boat cannot exceed too much what we already have in Clan heavies, its simply that they will have more armor but slower speed.
As it is now, Speed>>>>>>Armor when it comes to mechs, its why an Osiris can honestly have a better chance against a UAC20 Loki than a UAC Mauler can. To this point I'm not too impressed with Assault performance, not being able to work alone really hurts because they are really expensive so its hard to field more than one or two at a time. Also, both the Mauler and Awesome are just as fat and just as slow as the Atlas but have less armor, honestly at least for the Mauler, I wouldn't mind curbing its weapons down to add more armor overall.
Clan weapons do have drawbacks even if its something as simple as heat. Don't let the flat increase damage fool you.