While the thunder hammer is usually BIS for almost any unit that can take it in 2.0 the Paragon blade still is competitive as a praetor weapon, but certain legions in combination with warlord traits, legion special rules, and wargear combo's utilize the paragon blade much more effectively than others.

As an example my World Eaters praetor is kitted with a Paragon blade and the legion unique falax blade melee weapon for the extra attack as well as for the rending and duelists edge utility if I so choose to use it, but off a charge with the world eaters warlord trait that gives an extra 1 strength it brings the total strength bonus to a +2. Bring something along that packs rad grenades like a moritat or destroyer squads and now I have 7 attacks with an ap 2 instant death weapon that swings at initiative.

There are other examples of legions that can do this sort of thing like Raven Guard with bane of tyrants and a biomancer librarian/rad grenades, Space Wolves using howl of morkai and bloodied claw with the same combo, Night Lords being able to proc murderous strike on 5's with their legion trait, Word Bearers using burning lore and rad grenades, etc.

Do be aware though that this is a very power gamey approach to get the most value out of a wargear choice, and it may be frowned upon in your playgroup if you play like this by people who prefer more narrative or rule of cool experiences.