Paladins should run these, just like a Wyvern, by shooting and avoiding the wave attacks. The Exori con spell is of tremendous benefit here, so use it often. Likewise, Flash Arrows are well-suited to employ against this reptile. A level 37 paladin with 67 distance skill using a normal Bow can, for example, expect to use 13 of these energy arrows per kill, on average. As hatchlings are so stingy with their loot, and the cost of these specialized arrows so high, this is hardly economical, but it certainly makes for good power leveling. An alternative strategy is to come at them with Royal Spears and a very good Shield, e.g. 31 defense, and use Exori con continually. In any event, bring lots of Health and Mana potions, or expect to "wake up in the temple."
Knights will typically melee them and lure with caution, as other Frost Dragon Hatchlings and even Frost Dragons are found together. Skill 70/70 and a good one-handed weapon may help.