Many say she's a dumb healer cause amuse is treated as a buff, but with 2 heals + glancing debuff on 1st skill, she's still great for raids and is definitely recommended. She can be put at the frontline too with good runes but I will recommend putting her at the back as her 2nd skill heals based off her max hp.
Emma has a great AOE heal on her 3rd skill, but is only useful when max skilled cause of the long cd on her last skill. Her last skill also gives defence buff and extra heal will be topped up as a shield which helps. She also has glancing debuff on her first skill which is great.