tarting with the old TRO 3050 DC was more than equipped to fight clanners and later TROs just added to the arsenal of useful clan fighting mechs.
Of the top of my head:
Wolftrap-1
Phoenix Hawk-3K
Wolverine-7K
Grand Dragon-5K
Marauder-5D
later other good mechs are added:
Venom-9KA and later the -9KC
Wraith
Sunder A
Maelstrom-5K
Firestarter Omni B
Black Hawk KU Prime
Tessen
Ninja-Tos
No-dachis
etc.
Most of these mechs can keep pace with many clan mechs in their weight class. Since the Ursus is much more expensive than many of those IS mechs and lacks the stopping power at range, its not a question if the IS hordes can get into range, only when. And 16X armor is only going to last so long considering its on a 4/6 fast frame.
An Ursus costs 4.5 million and 1778 BV.
An Ursus II costs 8.9 million and 2069 BV.
Wolftrap-1 7.9 million and 1070 BV.
Phoenix Hawk-3K 8.2 million and 1359 BV.
Wolverine-7K 9.9 million and 1331 BV.
Grand Dragon-5K 13.3 million and 1358 BV.
Marauder-5D 15.8 million and 1787 BV.
I would comfortably put an Ursus against any of these 'Mechs and only expect a fair fight against the Marauder, as BV suggests.
They are more tactically mobile, but given you can put two Ursus in the field for the same price is that a problem? On a CBill balanced system if you commit any of these 'Mechs as a counter against an Ursus the Ursus has already won.
Venom-9KA and later the -9KC 6.3 million and 865 BV. 6.8 and 939BV.
Wraith 13 million and 1287BV
Sunder A 27 million and 2003BV
Maelstrom-5K 18 million and 1694BV
Firestarter Omni B 10.4 million and 1070BV
Black Hawk KU Prime 14.5 million and 1731BV
Tessen 10 million and 1243BV
Ninja-To 4 16.4 million and 1762BV
No-dachi 2K 17.8 million and 1739BV
This list is important for being illustrative. An IS 'Mech needs to be at least 60 tons and running an XL engine to get close to the combat effectiveness of an Ursus. That's Clantech for you. Heck given standard 3/4 pilots an Ursus out BVs a Sunder A (but the armour difference means the win will probably go to the Sunder.).
In several cases you can try and mis-position the Ursus, but if battle is joined the Ursus is at least equal.
On a 50 x 50 map a 4/6 'Mech needs to be away of where its Starmates are and what the objectives are, but that is nothing new and fairly standard for trooper 'Mechs. Also the Ursus' pulse lasers make jumpy jumpy 'Mechs like the Wraith have to take notice. Its not devastating, but those 'Mechs aren't as invulnerable as others.
I should point out the 4/6/6 movement of the Ursus II makes it comparably manoeuvrable to a Firestarter II or Tessen or PHawk and the BV increases accordingly, as does the price of the XL engine.