Quetzalcoatl.Commencal said:
»This is probably the slowest method and still a bit dangerous, I used the enspell strat on Rdm. It's hit or miss depending on whether it decides to cast Kaustra when Silence wears off, otherwise it's really easy. I had to stack magic accuracy to reduce enspell resistance.
I have been using this strategy on VD and I think I have found a way to largely reduce the risk of Kaustra by trying to use Silence only twice. The Silence at the beginning of the fight is casted with my standard magic accuracy + duration gear, with Crocea and Daybreak sheathed. At 51% HP I usually need to wait for some time until this Silence wears off. This allows the second Silence to be landed at 51% HP (BG wiki says it seems to cast Kaustra only under 50% HP).
To ensure the second Silence lasting for the remainder of the fight is the other key part of this strategy. I first cast a normal Silence with Chironic Hose to get one immunobreak (this is important). Then, I land the guaranteed Silence with both Stymie and Saboteur active. So far, this always lasts for the remainder of the fight. The fight takes about 10 minutes in total.
Note1: The relevance of that one immunobreak was recently discussed in length in the RDM forum here so I will avoid going into detail. Basically, without that immunobreak, a Stymie-forced Silence will be guaranteed to be half-resisted if the monster's Silence resistance rank is 5% (seemingly to be the case for the frog) or 10%.
Note2: in my case I have a GEO buffing me with Indi-Haste and Geo-Focus, and myself have Orpheus sash, but I think even without these, a RDM with decent gear can safely solo this using the above strategy.